<PAGE>

                                        HYBRID
                                    Networks, Inc.

                              PRODUCT PURCHASE AGREEMENT

THIS AGREEMENT ("Agreement") is made this 30th h of June, 1997 ("effective
date") by and between HYBRID NETWORKS, INC., "a California corporation";
("Hybrid") having its principal place of business at 10161 Bubb Road,
Cupertino, CA 95014 and RCN Operating Services, Inc., a New Jersey
corporation having its principal place of business at 105 Carnegie Center,
Princeton, New Jersey 08540("RCN")".

                                      RECITALS

Hybrid designs, develops, manufactures and distributes certain equipment
relating to high speed modem/routers for use in wireless and cable environments.

B.   RCN is a provider of communications and telecommunications services" in
     multiple markets in the United States, and has both mechanical and business
     expertise to make use of Hybrid products for the purpose of distributing
     data over "certain frequencies".

C.   RCN desires to purchase certain equipment from Hybrid, and Hybrid is
     willing to sell such equipment to RCN, on and subject to the terms set
     forth below.

Now, therefore, in consideration of the mutual agreements and covenants herein
contained, the parties, intending to be legally bound, agree as follows:

1.   SALE AND PURCHASE

A.   On and subject to the terms and conditions hereof, RCN intends to purchase
     from Hybrid, and Hybrid agrees to sell to RCN, a minimum of 25,000 units
     (the "Units") consisting of either Hybrid's model CCM-201/221 wireless and
     cable client cable modem/router (multi-user (which modems shall be capable
     of serving at least 20 users)) or N-201/221 modem (single user), or any
     combination thereof (the "Purchase Plan").  The Purchase Plan per-Unit
     price for the CCM-201/221 are identified in Addendum B (less the volume
     purchase agreement identified in Addendum C for the modems) RCN purchases
     are contingent on Hybrid's ability to provide products that are technically
     & price competitive, reliable, and can be delivered to meet RCN needs.

B.   RCN agrees to purchase from Hybrid by year end 12/31/97, and Hybrid
     agrees to sell to RCN a minimum of one thousand (1,000) Units and three
     (3) head-end sites plus an option for two (2)  additional sites, at
     designated prices per Addendum A. Purchase Plan includes all equipment
     purchased by AT&T that is installed in RCN systems, and all equipment
     purchased by Cable Michigan or Commonwealth Telephone.

C.   At the end of 1997, an additional discount or credit will be applied
     towards RCN's purchases for that year.  The discount is as follows:

                                                                         PAGE 1

<PAGE>

     $0-$500,000 = $15,000 credit
     $501,000-$750,000 = $30,000 credit
     $751,000 $1,000,000 = $45,000 credit
     >$1,000,000 = $50,000 credit

D.   RCN shall also have the right, but not the obligation to purchase
     additional equipment, identified on Addendum B, at its sole discretion.
     The purchase price for additional items (which are not included in the
     Purchase Plan) is contained in Addendum B (the Units and other items
     contained on Addenda A and B and the Software (as herein defined) are
     sometimes collectively referred to herein as the "Products").  Payment
     shall be made in accordance with Section 4 set forth below.  RCN shall be
     permitted to order either the CCM-201/221 or the N-201/221 with (i)
     encryption support (model numbers CCM-201/221-S and N-201/221-S) which will
     increase the per Unit price for each such Unit ordered by $100, and (ii) an
     internal telephone modem (currently in development), which will increase
     the per Unit price for each such Unit ordered by approximately $50 per
     Unit.  Hybrid shall notify RCN of the actual amount of the price increase
     prior to RCN placing any order for Units so configured.

E.   RCN agrees to take delivery of the Purchase Plan over a thirty-six month
     period, commencing on the Effective Date, and the parties agree to use
     their best efforts to develop a mutually agreed-upon forecasted delivery
     schedule not later than July 15, 1997 which schedule shall be revised on a
     quarterly basis not later than the 10th business days of each new quarter.

     F.   RCN shall order Products by issuing written purchase orders to Hybrid.
     Such purchase orders will be subject to written acceptance by Hybrid, and
     upon acceptance, will constitute a binding agreement between Hybrid and RCN
     with respect to the Products identified herein on the term and conditions
     included herein.  All purchase orders submitted by RCN to Hybrid shall be
     in English.  The terms and conditions of this Agreement will prevail over
     any inconsistent wording on purchase order forms.  Hybrid shall make best
     efforts to meet the quantities and shipping dates specified by RCN in each
     purchase order; however, Hybrid shall notify RCN within two (2) days
     following receipt of an order by Hybrid when quantities or shipping dates
     differ from those specified by RCN.  Hybrid's standard lead times of
     released products is 45 days after receipt of order.  Expedite requests
     will be handled on a case-by-case basis, Hybrid will make best effort to
     met RCN expedite requirements at no additional charge.

G.   Orders placed by RCN for Products will be accepted by Hybrid provided that:
     i)    order is signed by RCN authorized representative
     ii)   the order is received and accepted by Hybrid during the Term
     iii)  the value of any single order is not less than $500 and
     iv)   the order specifies the Products ordered, purchase price(s), exact
           "ship-to" and "bill-to" address and requested delivery schedule.

2.      TERM OF AGREEMENT

This Agreement shall come into force on the date first written above ("Effective
Date") and shall remain valid for orders placed and delivered during the period
of 36 months beginning on the Effective Date (the "term").

                                                                         PAGE 2

<PAGE>

3.    PRICES/TAXES
All purchase prices are exclusive of shipping and insurance charges which shall
be billed separately.  Installation and related charges are only included if
stated on the face of the order or quotation.  Installation and related charges
are subject to change due to RCN failure to complete site readiness as stated,
non-standard site conditions, force majeure events or RCN caused delays.  RCN
agrees to pay all such additional charges as invoiced by Hybrid only upon prior
written approval of RCN.

All prices are exclusive of all sales, use, excise, and other taxes, duties or
charges.  Unless evidence of tax exempt status is provided by RCN.  RCN shall
pay, or upon receipt of invoice from Hybrid, shall reimburse Hybrid for all such
taxes or charges levied or imposed on RCN, or required to be collected by
Hybrid, resulting from the Purchase Plan or any part thereof.

All prices are FOB Hybrid' Factory Cupertino, California, U.S.A. Unless
instructed otherwise.  Hybrid will arrange for insurance and standard commercial
shipping, the costs of which will be invoiced to the RCN.

RCN will be entitled to Preferred Customer status.  If, during the Term hereof,
Hybrid sells CCM-201/221 modem/router or N-201/221 single user modem (or the
encrypted version of either model) under similar or less advantageous (from
Hybrid's standpoint) terms and conditions to those paid by RCN, then the price
paid by RCN for all CCM Modem/routers that are on order to be delivered or any
future orders during the term of this agreement hereunder will be adjusted
downward to be equal to or below the lowest price at which Hybrid has sold said
Products.  Preferred Customer status only remains valid as long as RCN
procurements remain consistent with Purchase Plan over the Term hereof.  If
during the term hereof RCN chooses to purchase additional equipment above and
beyond the Purchase Plan, this Agreement will be amended accordingly based on
mutually agreed to terms and conditions provided. that such terms are no less
favorable than the terms set forth herein.

Prior to delivery, Hybrid reserves the right to make substitutions,
modifications and improvements to the Products, provided that such substitution,
modification or improvement shall not adversely affect performance in the
application originally agreed to with RCN, including, without limitation, any
substitution, modification or improvement that adversely affects a Product's
compatibility with the current Series 2000 system.

4.    PAYMENT/FINANCING
Terms of payment will be Net 30 days from date of shipment from Hybrid's
factory.  All amounts are payable to Hybrid Networks, Inc. at the address set
forth on the invoice.  RCN has a period of twenty (20) days after receipt of
Product within which to notify Hybrid in writing of any discrepancies in the
shipment that may give RCN the right to reject such shipment.

If RCN fails to satisfy Hybrid on payment arrangements, Hybrid may refuse to
accept an order or may allow RCN to make other arrangements satisfactory to
Hybrid prior to shipment.

5.   EQUIPMENT WARRANTY

                                                                         PAGE 3

<PAGE>

Hybrid warrants that all Hybrid manufactured equipment including any equipment
subcontracted by Hybrid that carries the Hybrid logo[ will be free from defects
of material and workmanship and [(] conform to manufacturer's published
specifications for a period of eighteen (18) months from the date of delivery
under normal operating conditions, which specifications are attached hereto as
Addendum H and incorporated herein by this reference.  Hybrid agrees to notify
RCN of any modification of any specifications relating to the Products, and
further agrees not to modify any such specifications in a manner that would
adversely affect the performance of the Products without prior written consent
of RCN.  Hybrid will assist RCN in any warranty matters with equipment not
manufactured for or by Hybrid Technologies but provided to RCN by Hybrid.

Should a product fail within this warranty period, Hybrid will repair or
replace, at its discretion, the defective product when it is returned to
Hybrid, shipping prepaid. Replacement products may be refurbished or contain
refurbished materials.  Proof of date of delivery of the returned product is
required.  Hybrid' sole obligation shall be to repair, replace, or refund the
purchase price, at its option.  Replacement Equipment may be new, refurbished
or remanufactured: provided, however, that any Replacement Equipment provided
by Hybrid to replace failed equipment upon initial installation thereof shall
be new.  Returned replaced Equipment shall become Hybrid' property.
Replacement Equipment shall be warranted for the unexpired portion of the
returned Equipment's warranty. The warranty provided under this section,
shall not apply to any item of the equipment which has been altered or
modified including any change, addition, or improvement.  Hybrids' sole
warranty liability to RCN with respect to equipment manufactured by a third
party that does not reside in Hybrid's current price list (in Addendum B).
and incorporated into Hybrid equipment shall be to pass through to RCN such
original equipment manufacturer's available product warranty.  The warranty
provided herein does not cover damage, defects, malfunctions or service
failures caused by:

a)   RCN's failure to follow Hybrid' environmental, installation, operation or
     maintenance specifications or instructions:
b)   Modifications, alterations or repairs made other than by Hybrid:
c)   RCN's mishandling, abuse, misuse, negligence, or improper storage,
     servicing or operation of the Equipment (including without limitation use
     with incompatible equipment).  Addendum I includes a written list of
     compatible equipment to the Hybrid PoP equipment, which list will be
     updated by Hybrid from time to time. : or
d)   Power failures, surges, fire, flood, accident, actions of third parties or
     other like events outside Hybrid' control.  Repairs necessitated during the
     warranty period by any of the foregoing causes may be made by Hybrid, and
     the RCN shall pay Hybrid' standard charges for time and materials, together
     with all shipping and handling charges arising from such repairs.

THIS WARRANTY CONSTITUTES HYBRIDS' SOLE AND EXCLUSIVE LIABILITY HEREUNDER.  AND
RCN'S SOLE AND EXCLUSIVE REMEDY FOR DEFECTIVE OR NONCONFORMING ITEMS AND IS IN
LIEU OF ALL OTHER WARRANTIES, EXPRESS,  IMPLIED OR STATUTORY (INCLUDING THE
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE).



6.   SOFTWARE

                                                                         PAGE 4

<PAGE>

(a)  LICENSE.  In connection with the purchase of the Units, Hybrid with its
     requisite power and authority, grants to RCN a non-exclusive,
     non-transferable, license to use the software and related documentation
     ("Software") based on the following conditions:

     I.   for up to 500 subscribers per PoP purchased by CUSTOMER pursuant to
          Section 1(F) is included in the original system purchase price
     II.  for total number of subscribers ranging from 501-3,000, RCN will pay
          $10 per subscriber or a one time fee of $25,000
     III. Once RCN has reached the 3,000 subscriber level per PoP, no
          additional software fees will charged.

Please note that the Software may include software and documentation that are
owned by third parties and distributed by Hybrid under license from the owner.

(b)  COPIES.  RCN shall not make any copies of the Software, except for a single
     archival copy solely for internal purposes.

(c)  CONFIDENTIALITY.  RCN shall maintain the confidentiality of the Software
     and shall not sublicense, sell, rent, disclose, make available,
     disassemble, or otherwise communicate the Software to any other person, or
     use the Software except as expressly authorized in writing by Hybrid.

(d)  TITLE.  The Software and all copies thereof will at all times remain the
     sole and exclusive property of Hybrid or its licensor, as applicable, and
     RCN shall obtain no title to the Software.

(e)  COPYRIGHT.  RCN shall reproduce all copyright notices and any other
     proprietary legends on any copy of the Software made by RCN.

(f)  ALTERATION.  RCN shall not modify, disassemble, or decompile the Software.

(g)  WARRANTY.  Hybrid does not warrant that the operation of the Software will
     be error free.  Hybrid will use reasonable efforts to correct any defects
     reported to Hybrid in writing within 90 days of the date of shipment,
     exclusive of defects caused by physical defects in Software disks due to
     mishandling, operator error or interfacing other systems not approved by
     Hybrid.

(h)  Maintenance and enhancement releases occurring during the Term of this
     Agreement will automatically be sent to RCN at no additional charge.

"Hybrid warrants that is has full power and authority to lawfully grant the
rights granted by this Agreement, without the consent of any other person,
entity or governmental authority, and that, TO THE BEST OF HYBRID'S KNOWLEDGE
the use by Customer of the Software (including the copying thereof) and the
Products shall not in any way constitute an infringement or other violation
of any copyright, trade secret, trademark, patent, proprietary information,
nondisclosure, intellectual property or other rights of any party.  Hybrid
shall indemnify, defend, and hold harmless RCN, its affiliates and
subsidiaries and all officers, directors, employees, and agents of such
corporations from and against any and all claims, actions, losses,
liabilities, damages, costs, and expenses, including attorney fees, arising
out of or relating to any breach of the representations and warranties of
this subsection, PROVIDED THAT HYBRID SHALL BE GIVEN (i)

                                                                         PAGE 5

<PAGE>

EXPRESS, IMPLIED OR STATUTORY (INCLUDING THE WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR PURPOSE).

7.     TRAINING

RCN will receive two (2) "free" slots for initial training for each PoP
purchased with annual updates as required.  Accumulation of free training slots
only remains valid so long as this Agreement remains in effect.

8. RIGHTS OF THE PARTIES

HYBRID RIGHTS-RCN AGREES TO:
a)   Issue a national scale press release announcing its purchase of Hybrid
     equipment.  RCN agrees to issue a national press release announcing the
     commercial data delivery service in each city using Hybrid as soon as
     practicable after launch of such service.  In addition,  RCN agrees to
     issue periodic press release promoting the development of its commercially
     available data service using Hybrid equipment.  During the installation
     period, both Hybrid and RCN will have the right of review and approval,
     which will not be unreasonably withheld, of any press release that the
     other party proposes to issue describing the service and equipment.

B)   Permit Hybrid to visit each cities facility in the RCN system where Hybrid
     equipment (listed in ADDENDUM A) is located and showcase the technology and
     business model for other prospective customers, investors or partnering
     prospects selected by Hybrid.  RCN will be given reasonable advance notice
     of these visits and they will occur only during normal business hours.
     Hybrid agrees to indemnify and hold RCN harmless for any claim, loss or
     liability incurred or made or asserted against RCN (including reasonable
     fees and disbursements of counsel defending itself against such claims,
     losses of liabilities) in connection with the rights granted to Hybrid
     pursuant to this Section: provided, however, there shall be no obligation
     of Hybrid to so indemnify RCN hereunder if the claim, loss or liability
     arises solely out of the gross negligence or willful misconduct of RCN.

c)   Hybrid and RCN will meet quarterly to review status of Purchase Plan and to
     forecast upcoming shipments.  CCM commitments are for unit purchases only
     and that RCN has the right to manage unit orders among the CCM models
     contracted.  If Hybrid introduces new CCM models during the terms of this
     Agreement,  RCN has the right to apply the new models against volume
     commitments based on mutually agreed to discounts.

d)   RCN will receive two (2) Single User CCMs free of charge for every new
     Hybrid PoP that is purchased.

e)   Hybrid will develop and support software tools that will allow for network
     monitoring and simplified installation ("Golden Install").  These tools
     will be phased into Hybrid's system beginning with the next software
     release, Hybridware release 4.2.


RCN RIGHTS - HYBRID AGREES TO:
a)   Upgrade all FSK modems (P/N CCM-221 and N-221) to QPSK immediately upon
     general release.

                                                                         PAGE 6

<PAGE>

b)   RCN will receive preferential treatment in regards to advance releases of
     software for the purpose of jointly testing and evaluating said software.
     Hybrid will make best efforts to keep RCN informed of future releases.  In
     return,  RCN will report system errors and problems on a timely basis to
     Hybrid.

c)   A joint marketing effort - for every one-hundred (100) Hybrid modems
     purchased by RCN, Hybrid will Donate one (1) modem (model to be agreed to
     by both parties)to a designated educational institution.
d)   RCN has the right to "co-label" Hybrid modems and will be responsible for
     all expenses associated.

9.   SYSTEM/SOFTWARE SUPPORT
RCN will receive free of charge "System support" as outlined in ADDENDUM D, for
all head end location sites during the first six (6) months following the
delivery of the units in these markets.  After this period, an "Annual System
Support Contract" may be purchased by RCN at the rate set forth in Addendum D.

Hybrid will support the Series 2000 product line with Technical Support and
spare parts for the Term hereof.

Hybrid will follow the "Trouble ticket Process & Clearing" as outlined in
ADDENDUM E. If these procedures are changed,  Hybrid will notify RCN in writing
prior to the effective date of such change.

Hybrid will follow the "Escalation Procedures" as outlined in ADDENDUM F. If
these procedures are changed,  Hybrid will notify RCN in writing prior to the
effective date of such change.

10. TECHNICAL SPECIFICATIONS
System functionality is limited to the published "Hybrid Series 2000 - System
Description".  A copy of said manual has been forwarded to RCN.

Hybrid shall complete the installation services in accordance with Hybrids'
normal installation practices.  Hybrid shall perform its standard acceptance
testing as outlined on ADDENDUM G, on the installed Equipment and RCN agrees to
monitor said testing.  Upon completion of installation, as described above,
Hybrid shall notify RCN that the Equipment has been installed and operates in
accordance with applicable test and performance specifications.  The date of
such notification shall be the installation cutover date.  Hybrid may at its
sole discretion use subcontractors to provide installation services.

11. EXCUSABLE DELAY
Notwithstanding anything contained in this Agreement to the contrary, neither
party shall be liable to the other for failure to perform any obligation under
this Agreement (nor shall any charge or payments be made in respect thereof) if
prevented from doing so by reason of acts of God, strikes, labor unrest,
embargoes, civil commotion, rationing or other

governmental orders or requirements, acts of civil or military authorities,
or other contingencies if and to the extent such cause is beyond the
reasonable control of such party

                                                                         PAGE 7

<PAGE>

and all requirements as to notice, another performance required hereunder within
a specified period, shall be automatically extended to accommodate the period of
any such cause which shall interfere with such performance.


12. CHANGE, CANCELLATION, AND TERMINATION
In the event that either party breaches any provision of this Agreement and
fails to cure such breach within thirty (30) days after written notice from
the other party, the breaching party shall be in default and the
non-breaching party shall have the right, but not the obligation, to
terminate this Agreement by providing written notice to the breaching party
at least thirty (30) days prior to the date of termination.  Any subsequent
cure of the breach that resulted in the termination notice will not affect
the validity of the termination notice, unless such notice is withdrawn by
the non-breaching party.

13. ASSIGNMENT
Neither party may assign this Agreement in whole or in part without the prior
written consent signed by an officer of the other party, which consent shall not
be unreasonably withheld; provided, however, that RCN shall be permitted to
assign this Agreement, in whole or in part, with notice, but without the
necessity of consent, to any of its affiliates (defined in Rule 12b-2 of the
Security Exchange Act of 1934, as amended).

14. GOVERNING LAW, VENUE, AND JURISDICTION
This Agreement will be governed by and construed in accordance with the laws of
the "State of New Jersey", "State of New York",  "State of Michigan",
"Commonwealth of Pennsylvania", or "Commonwealth of Massachusetts".  Reasonable
attorney fees shall be reimbursed, with respect to the foregoing, to the party
who prevails on the merits.

15. ENFORCEABILITY
If any provision of this Agreement shall be held to be invalid, illegal or
unenforceable, the validity, legality or enforceability of the remaining
provisions shall in no way be affected or impaired.

16. NOTICES
Any notice required to be given by either party to the other party shall be in
writing and shall be deemed given if personally delivered, if sent by facsimile
(with receipt acknowledged) to the facsimile number the other party set forth
below or if mailed postage prepaid, to:

     Hybrid Networks, Inc.       RCN Telecom Services, Inc.
     10161 Bubb Road             105 Carnegie Center
     Cupertino, CA 95014         Princeton, New Jersey 08540
     Attention: Jeff Gates       Attention: Mark Haverkate
     Fax no. 408/725-2439        Fax no. 609-734-7521


     or such other address as the party to which the notice is sent shall have
     provided to the other party by written notice in accordance with this
     Section.


                                                                         PAGE 8

<PAGE>

17. LIMITATION OF LIABILITY
NOTWITHSTANDING ANY OTHER PROVISIONS OF THIS CONTRACT,  UNDER NO CIRCUMSTANCES
SHALL either party BE LIABLE TO the other party OR ANY THIRD PARTY FOR SPECIAL,
INCIDENTAL,  INDIRECT OR CONSEQUENTIAL DAMAGES, AS A RESULT OF A BREACH OF ANY
PROVISION OF THIS CONTRACT.  Each party (the "Indemnifying Party") HEREBY
INDEMNIFIES the other party (the "Indemnified Party") AGAINST ALL LOSS OR
LIABILITY FROM CLAIMS ARISING OUT OF OR RELATING TO THE INSTALLATION, OPERATION,
OR USE OF THE EQUIPMENT, WHETHER ON ACCOUNT OF NEGLIGENCE OR OTHERWISE;
PROVIDED, HOWEVER, the Indemnifying Party shall have no obligation to indemnify
the Indemnified Party for any loss of liability arising out of Indemnified
Party's GROSS NEGLIGENCE OR WILLFUL MISCONDUCT.

18. ENTIRE AGREEMENT
This Agreement supersedes all previous communications, transactions, and
understandings, whether oral, or written, and constitutes the sole and entire
agreement between the parties pertaining to the subject matter hereof.  No
modification or deletion of, or addition to these terms shall be binding on
either party unless made in writing and signed by a duly authorized
representative of both parties.

19. "CONFIDENTIAL INFORMATION

Hybrid hereby acknowledges that during the course of performing the services
under this Agreement, it may come into possession of confidential information
which may not be disclosed to any third party.  Further, Hybrid agrees not to
disclose said information to any person other than on a need-to-know basis.
Confidential information shall include, but is not limited to, any
information concerning RCN's business and affairs, inventory, improvements,
process, techniques, contracts with third party and other trade secrets
obtained during the term of this Agreement. INFORMATION WILL NOT BE SUBJECT
TO THIS PROVISION IF IT IS OR BECOMES A MATTER OF PUBLIC KNOWLEDGE WITHOUT
THE FAULT OF HYBRID, IF IT WAS A MATTER OF WRITTEN RECORD IN HYBRID'S FILES
PRIOR TO DISCLOSURE BY RCN, OR IF IT WAS RECEIVED BY HYBRID FROM A THIRD
PERSON UNDER CIRCUMSTANCES PERMITTING ITS DISCLOSURE BY HYBRID The terms of
this subsection shall survive the termination of this Agreement
FOR A PERIOD OF THREE YEARS."

In Witness Whereof, duly authorized representatives of the Parties, hereto have
executed this Agreement as of the day and year first above written.

Hybrid Networks, Inc.       RCN:

By: /s/ [ILLEGIBLE]         By: /s/ [ILLEGIBLE]
   ------------------------   ------------------------
Title:  Chm & CEO           Title:  EVP
      ---------------------       --------------------
Date:  5 Aug 1997           Date:  July 31, 1997
     ----------------------      ---------------------

                                                                         PAGE 9


<PAGE>

                              ADDENDUM A

                   FIRST FIVE SITES - 1997 SHIPMENTS

                             ALLENTOWN SITE

               SERIES 2000 - CABLE DOWN (64QAM), TELEPHONE AND ROUTER
               RETURN
<TABLE>
<CAPTION>
===================================================================================================================================
  PRODUCT                                                              CONFIGURATION                 PRICE     QUANTITY
                                                                       -------------------------
   CODE                             COMPONENT                               MIN         MAX          (US$)
===================================================================================================================================

         HYBRID PoP EQUIPMENT, SOFTWARE LICENSES AND SPARE PARTS
<C>          <S>                                                        <C>       <C>              <C>             <C>   <C>
-----------------------------------------------------------------------------------------------------------------------------------
  CMG-2000     CyberManager 2000 with HybridWare + SW for 500 Subcribers      1           1           25,000          1      XXX
-----------------------------------------------------------------------------------------------------------------------------------
  SNL-0500     Subscriber 500 Network License (see Note 1)                           As Required       5,000                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
  SNL-2500     Subscriber 2500 Network License (see Note 1)                          As Required      25,000                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
  CMD-2000     CM Downstream Router with HybridWare + SW                      1      As Required      18,170          1      XXX
-----------------------------------------------------------------------------------------------------------------------------------
  SEC-010      Secure Encryption Card (DES)                                                              895          1      XXX
-----------------------------------------------------------------------------------------------------------------------------------
 SQC-200-3     SIF (QAM) Card, 3-channel (each 10 Mbps)                       1       2 per CMD        4,150          2      XXX
-----------------------------------------------------------------------------------------------------------------------------------
 QMC-200-3     64 QAM Modulator Card w/Filter & Combiner, 3 Channel           1       2 per CMD        4,820          2      XXX
-----------------------------------------------------------------------------------------------------------------------------------
 HFL-2220      IF Filter (standalone, special purpose)                     NOTE 2     2 per CMD          POA                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
CMU-2000-8T    CM Upstream Router with HybridWare + SW                        1      As Required      18,285                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
 TDC-001-8     Phone Demodulator Card, 8 lines per card                       1       8 per CMU        3,095                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
               COMMERCIAL PoP EQUIPMENT ALSO AVAILABLE FROM HYBRID

               (TYPICAL PRICES, NO DISCOUNTS, PRICES MAY CHANGE WITHOUT
               NOTICE)
-----------------------------------------------------------------------------------------------------------------------------------
  OFS-200      Fast Ethernet Switch (Cisco Catalyst 2900)                     1                       17,500              $  XXX
-----------------------------------------------------------------------------------------------------------------------------------
  OCM-160      C6M Modulator/Upconverter (USA Spec)                           1        NOTE 3          2,140                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
  OCM-165      C6MP Modulator/Upconverter (USA Spec)                          1       NOTE 3,4         2,950                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
  OCM-260      C6U Modulator/Upconverter (USA and International)              1        NOTE 3          2,950                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
               APONET BANDWIDTH MANAGER (MODEL 10)                                                     5,000          1      XXX
-----------------------------------------------------------------------------------------------------------------------------------
  OCM-400      IP Gateway Router (Cisco 7206)                                                         13,000          1   $  XXX
-----------------------------------------------------------------------------------------------------------------------------------
  OCM-401      TI DSU (Generic Internet Connection)                                                    1,250          1      XXX
-----------------------------------------------------------------------------------------------------------------------------------
  ORK-719      7-foot, 19-inch rack                                           1                          940                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
  CKT-201      Baseline One-Way Cable/Telephone System Cabling Kit      1 (or equiv)                     100                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
  DKT-030      Monitor and Keyboard (both rackmount for CMD and CMU)          1      As Required         925          1      XXX
-----------------------------------------------------------------------------------------------------------------------------------
  OPS-030      Power Strip                                                           As Required         130                 XXX
-----------------------------------------------------------------------------------------------------------------------------------



                                                                       PAGE 10
<PAGE>


               SPARE PARTS

-----------------------------------------------------------------------------------------------------------------------------------
  LAC-010      10/100 BaseT LAN Interface Card                                                           690                 XXX
-----------------------------------------------------------------------------------------------------------------------------------


               HYBRID CLIENT CABLE MODEMS

-----------------------------------------------------------------------------------------------------------------------------------
  CCM-201      Client Cable Modem (multi-user)                                       As Required         540        100      XXX
-----------------------------------------------------------------------------------------------------------------------------------
 CCM-201-S     Client Cable Modem (multi-user), encryption support (DES)             As Required         640                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
   N-201       Client Cable Modem (single-user)                                      As Required         295        100   $  XXX
-----------------------------------------------------------------------------------------------------------------------------------
  N-201-S      Client Cable Modem (single-user), encryption support (DES)            As Required         395                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
               COMMERCIAL CABLE MODEM ACCESSORIES

               (TYPICAL PRICES, NO DISCOUNTS, PRICES MAY CHANGE WITHOUT
               NOTICE, RECOMMEND LOCAL PURCHASE)
-----------------------------------------------------------------------------------------------------------------------------------
  OTM-001      V.34 28.6 Phone Modem (typically US Robotics)                         As Required         125        200   $  XXX
-----------------------------------------------------------------------------------------------------------------------------------
  CBL-001      RS-232 Modem Cable (see Note 5)                                       As Required           8        200      XXX
-----------------------------------------------------------------------------------------------------------------------------------
  OEH-005      Ethernet Hub (5-port support for five computers)                      As Required          80          0      XXX
-----------------------------------------------------------------------------------------------------------------------------------
               HYBRID TECHNICAL SUPPORT AND TRAINING (SEE NOTE 6)

-----------------------------------------------------------------------------------------------------------------------------------
TRN-201-4C     One-Way Cable (64QAM) Training Program                         1        REQUIRED      N/C              2      XXX
-----------------------------------------------------------------------------------------------------------------------------------
TRN-201-1C     One-Way Cable (64QAM) Training Program/Per Student                    As Required       1,500                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
 SRV-100       System Integration per Day                                            As Required       1,500                 XXX
-----------------------------------------------------------------------------------------------------------------------------------


                                                                                                                 TOTAL:     $20X
===================================================================================================================================
</TABLE>

Notes:

           1 Price as listed when purchased with the CMG-2000
           2 Standalone filter may be required in remote fiber links using a
             channel translator
           3 One c6m is required per downstream carrier frequency; one
             C6U is required per 2 downstream
             carrier frequencies
           4 Special order from General Instruments
           5 RS-232 modem cables are bulk shipped, used to connect cable
             modem and telephone modem.
           6 Training program prices are for Cupertino Training; additional
             costs apply to on-site training.



                                                                       PAGE 11
<PAGE>

                                   BOSTON SITE

               SERIES 2000 - CABLE DOWN (64QAM), TELEPHONE AND ROUTER
               RETURN
<TABLE>
<CAPTION>
===================================================================================================================================
  PRODUCT                                                              CONFIGURATION                 PRICE     QUANTITY
                                                                       -------------------------
   CODE                             COMPONENT                               MIN         MAX          (US$)
===================================================================================================================================

         HYBRID PoP EQUIPMENT, SOFTWARE LICENSES AND SPARE PARTS
<C>          <S>                                                        <C>       <C>              <C>             <C>   <C>
-----------------------------------------------------------------------------------------------------------------------------------
 CMG-2000      CyberManager 2000 with HybridWare + SW for 500 Subscribers     1           1           25,000          1      XXX
-----------------------------------------------------------------------------------------------------------------------------------
 SNL-0500      Subscriber 500 Network License (see Note 1)                           As Required       5,000                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
 SNL-2500      Subscriber 2500 Network License (see Note 1)                          As Required      25,000                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
 CMD-2000      CM Downstream Router with HybridWare + SW                      1      As Required      18,170          1      XXX
-----------------------------------------------------------------------------------------------------------------------------------
 SEC-010       Secure Encryption Card (DES)                                                              895          1      XXX
-----------------------------------------------------------------------------------------------------------------------------------
SQC-200-3      SIF (QAM) Card, 3-channel (each 10 Mbps)                       1       2 per CMD        4,150          2      XXX
-----------------------------------------------------------------------------------------------------------------------------------
QMC-200-3      64 QAM Modulator Card w/Filter & Combiner, 3 Channel           1       2 per CMD        4,820          2      XXX
-----------------------------------------------------------------------------------------------------------------------------------
 HFL-2220      IF Filter (standalone, special purpose)                     NOTE 2     2 per CMD         POA                  XXX
-----------------------------------------------------------------------------------------------------------------------------------
CMU-2000-8T    CM Upstream Router with HybridWare + SW                        1      As Required      18,285                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
TDC-001-8      Phone Demodulator Card, 8 lines per card                       1       8 per CMU        3,095                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
               COMMERCIAL PoP EQUIPMENT ALSO AVAILABLE FROM HYBRID

               (TYPICAL PRICES, NO DISCOUNTS, PRICES MAY CHANGE WITHOUT
               NOTICE)
-----------------------------------------------------------------------------------------------------------------------------------
 OFS-200       Fast Ethernet Switch (Cisco Catalyst 2900)                     1                       17,500          1   $  XXX
-----------------------------------------------------------------------------------------------------------------------------------
 OCM-160       C6M Modulator/Upconverter (USA Spec)                           1        NOTE 3          2,140                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
 OCM-165       C6MP Modulator/Upconverter (USA Spec)                          1       NOTE 3,4         2,950                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
 OCM-260       C6U Modulator/Upconverter (USA and International)              1        NOTE 3          2,950                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
               Aponet Bandwidth Manager (Model 10)                                                     5,000          1      XXX
-----------------------------------------------------------------------------------------------------------------------------------
 OCM-400       IP Gateway Router (CISCO 7206)                                                         13,000          1   $  XXX
-----------------------------------------------------------------------------------------------------------------------------------
 OCM-401       TI DSU (generic internet connection)                                                    1,250          1      XXX
-----------------------------------------------------------------------------------------------------------------------------------
 ORK-719       7-foot, 19-inch rack                                           1                          940                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
 CKT-201       Baseline One-Way Cable/Telephone System Cabling Kit       1 (or equiv)                    100                 XXX
-----------------------------------------------------------------------------------------------------------------------------------
 DKT-030       Monitor and Keyboard (both rackmount for CMD and CMU)          1      As Required         925          1      XXX
-----------------------------------------------------------------------------------------------------------------------------------
 OPS-030       Power Strip                                                           As Required         130                 XXX
-----------------------------------------------------------------------------------------------------------------------------------

               SPARE PARTS
-----------------------------------------------------------------------------------------------------------------------------------
 LAC-010       10/100 BaseT LAN Interface Card                                                          690                  XXX
-----------------------------------------------------------------------------------------------------------------------------------

                                                                       PAGE 12

<PAGE>


               HYBRID CLIENT CABLE MODEMS

-----------------------------------------------------------------------------------------------------------------------------------
  CCM-201      Client Cable Modem (multi-user)                                       As Required        540         100      XXX
-----------------------------------------------------------------------------------------------------------------------------------
 CCM-201-S     Client Cable Modem (multi-user), encryption support (DES)             As Required        640                  XXX
-----------------------------------------------------------------------------------------------------------------------------------
   N-201       Client Cable Modem (single-user)                                      As Required        295         100      XXX
-----------------------------------------------------------------------------------------------------------------------------------
  N-201-S      Client Cable Modem (single-user), encryption support (DES)            As Required        395                  XXX
-----------------------------------------------------------------------------------------------------------------------------------
               COMMERCIAL CABLE MODEM ACCESSORIES

               (TYPICAL PRICES, NO DISCOUNTS, PRICES MAY CHANGE WITHOUT
               NOTICE, RECOMMEND LOCAL PURCHASE)
-----------------------------------------------------------------------------------------------------------------------------------
  OTM-001      V.34 28.8 Phone Modem (typically US Robotics)                         As Required        125         200      XXX
-----------------------------------------------------------------------------------------------------------------------------------
  CBL-001      RS-232 Modem Cable (see Note 5)                                       As Required          8         200      XXX
-----------------------------------------------------------------------------------------------------------------------------------
  OEH-005      Ethernet Hub (5-port support for five computers)                      As Required         80           0      XXX
-----------------------------------------------------------------------------------------------------------------------------------
               HYBRID TECHNICAL SUPPORT AND TRAINING (SEE NOTE 6)

-----------------------------------------------------------------------------------------------------------------------------------
TRN-201-4C     One-Way Cable (64QAM) Training Program                         1       Required      N/C               2      XXX
-----------------------------------------------------------------------------------------------------------------------------------
TRN-201-1C     One-Way Cable (64QAM) Training Program/Per Student                    As Required      1,500                  XXX
-----------------------------------------------------------------------------------------------------------------------------------
 SRV-100       System Integration per day                                            As Required      1,500                  XXX
-----------------------------------------------------------------------------------------------------------------------------------



                                                                                                                  TOTAL:    $2XX
===================================================================================================================================
</TABLE>

Notes:

           1 Price as listed when purchased with the CMG-2000.
           2 Standalone filter may be required in remote fiber links using a
             channel translator.
           3 One C6M is required per downstream carrier frequency; one
             C6U is required per 2 downstream
             carrier frequencies.
           4 Special order from General Instruments.
           5 RS-232 modem cables are bulk shipped, used to connect cable
             modem and telephone modem.
           6 Training program prices are for Cupertino Training; additional
             costs apply to on-site training.





                                                                       PAGE 13
<PAGE>

  Series 2000 - Cable (64QAM) Down, Cable (FSK) Return - Manhattan, N.Y.

               (To be completed pending AT&T participation)







                                                                       PAGE 14
<PAGE>

    Series 2000 - Cable (64QAM) Down, Cable (FSK) Return - Carmel, N.Y.

               (To be completed pending AT&T participation)







                                                                       PAGE 15
<PAGE>

  Series 2000 - Cable (64QAM) Down, Cable (FSK) Return - Princeton, N.J.

               (To be completed pending AT&T participation)








                                                                       PAGE 16
<PAGE>

                                   ADDENDUM B

                                GLOBAL PRICE LIST
<TABLE>
<CAPTION>
PoP EQUIPMENT
<S>             <C>                                                         <C>
----------------------------------------------------------------------------------------------
  CMG-2000      CyberMngr 2000 w\HybridWare + SW for 500 Subs.                      $25,000
----------------------------------------------------------------------------------------------
  SNL-0500      Subscriber 500 Network License                                       $5,000
----------------------------------------------------------------------------------------------
  SNL-2500      Subscriber 2500 Network License                                     $25,000
----------------------------------------------------------------------------------------------
  CMD-2000      CM Downstream Router with Hybridware + SW                           $18,170
----------------------------------------------------------------------------------------------
  SEC-010       Secure Encryption Card (DES)                                          $895
----------------------------------------------------------------------------------------------
 SQC-200-3      SIF (QAM) Card, 3-channel (each 10 Mbps)                             $4,150
----------------------------------------------------------------------------------------------
  SVC-100       4VSB 3-Ch SIF Card                                                   $4,150
----------------------------------------------------------------------------------------------
  HEM-2004      Encoder/Modulator (4-VSB)                                            $3,200
----------------------------------------------------------------------------------------------
 QMC-200-3      64 QAM Modulator Card w/ Filter & Combiner, 3 channel                $4,820
----------------------------------------------------------------------------------------------
QMC-200-3C      64 QAM Modulator Card w/ Combiner, 3 channel                         $4,820
----------------------------------------------------------------------------------------------
HEM-2004-B      Baseband Transmitter (IF-to BB)                                      $2,600
----------------------------------------------------------------------------------------------
HEM-2004-I      Baseband Receiver (BB to IF)                                         $3,400
----------------------------------------------------------------------------------------------
HEM-2004-B      Encoder-Baseband (64 QAM)                                            $2,600
----------------------------------------------------------------------------------------------
HEM-2204-I      Modulator-IF (64-QAM)                                                $3,400
----------------------------------------------------------------------------------------------
 HFL-2220       IF Filter (standalone, special purpose)                                POA
----------------------------------------------------------------------------------------------
CMU-2000-8T     CM Upstream Router with HybridWare + SW                             $18,285
----------------------------------------------------------------------------------------------
CMU-2000-14C    CM Upstream Router with HybridWare + SW                             $18,860
----------------------------------------------------------------------------------------------
 VDC-010-2      4-VSB Demodulator Card, 2 channels per card                          $2,595
----------------------------------------------------------------------------------------------
 VBU-010-x      Hybrid Block Upconverter                                             $3,200
----------------------------------------------------------------------------------------------
  CKT-201       Baseline One-Way System Cabling Kit                                   $100
----------------------------------------------------------------------------------------------
 TDC-001-8      Phone Modem Card, 8 lines per card                                   $3,095
----------------------------------------------------------------------------------------------
 CSM-2000       CyberSecure 2000, includes HybridWare + SW                          $15,000
----------------------------------------------------------------------------------------------
 SUG-2000       Software Upgrade from Series 2000 ELS to full Series 2000             $500
----------------------------------------------------------------------------------------------


<CAPTION>
COMMERCIAL PoP EQUIP. AVAILABLE FROM HYBRID
<S>             <C>                                                         <C>
----------------------------------------------------------------------------------------------
  OFS-200       Fast Ethernet Switch (Cisco Catalyst 2800)                           $8,700
----------------------------------------------------------------------------------------------
  OCM-160       C6M Modulator/Upconverter (USA Spec)                                 $2,140
----------------------------------------------------------------------------------------------
  OCM-165       C6MP Modulator/Upconverter (USA Spec)                                $2,950
----------------------------------------------------------------------------------------------
  OCM-260       C6U Modulator/Upconverter (USA and International)                    $2,950
----------------------------------------------------------------------------------------------
  ORK-719       7-foot, 19-inch rack                                                  $940
----------------------------------------------------------------------------------------------
  CKT-201       Baseline One-Way Cable/Telephone System Cabling Kit                   $100
----------------------------------------------------------------------------------------------
  CKT-221       Baseline Two-Way Cable (FSK) System Cabling Kit                       $200
----------------------------------------------------------------------------------------------
  DKT-030       Monitor and Keyboard  (both rackmount for CMD AND CMU)                $925
----------------------------------------------------------------------------------------------
  OCS-016       16-way Splitter                                                        $0
----------------------------------------------------------------------------------------------
  ODF-260       Diplex Filter                                                          $0
----------------------------------------------------------------------------------------------




                                                                       PAGE 17
<PAGE>

----------------------------------------------------------------------------------------------
  OPS-030       Power Strip                                                          $130
----------------------------------------------------------------------------------------------
  OLP-330       Termianl Server (Portmaster) 30 Port                                $3,700
----------------------------------------------------------------------------------------------
 OEX-020-7      Upstream Demodulator Shelf (supports 7 FSK cards)                   $2,200
----------------------------------------------------------------------------------------------
  OEC-021       FSK Upstream Demodulator Card                                        $965
----------------------------------------------------------------------------------------------

<CAPTION>
SPARE PART
<S>             <C>                                                         <C>
----------------------------------------------------------------------------------------------
  LAC-010       10/100 BaseT LAN Interface Card                                      $690
----------------------------------------------------------------------------------------------
  HSB-210-S     Secure Encryption Card (SBUS)                                        $895
----------------------------------------------------------------------------------------------

<CAPTION>
HYBRID CLIENT CABLE MODEMS* - MAYBE SUPERCEDED BY VPA
<S>             <C>                                                         <C>
----------------------------------------------------------------------------------------------
  CCM-101       Client Cable Modem                                                   $995
----------------------------------------------------------------------------------------------
 CCM-101-S      Client Cable Modem, encryption support (DES)                        $1,095
----------------------------------------------------------------------------------------------
  CCM-161       CCM (4-VSB), ELS (Series 2000 compatible)                            $995
----------------------------------------------------------------------------------------------
 CCM-161-S      CCM (4-VSB), ELS encryption support (DES)                           $1,095
----------------------------------------------------------------------------------------------
  CCM-201       Client Cable Modem (multi-user)                                      $795
----------------------------------------------------------------------------------------------
 CCM-201-S      Client Cable Modem (multi-user), encryption support (DES)            $895
----------------------------------------------------------------------------------------------
  CCM-221       Client Cable Modem                                                   $845
----------------------------------------------------------------------------------------------
 CCM-221-S      Client Cable Modem, encryption support (DES)                         $945
----------------------------------------------------------------------------------------------
   N-201        Client Cable Modem (single-user)                                     $440
----------------------------------------------------------------------------------------------
  N-201-S       Client Cable Modem (single-user), encryption support (DES)           $540
----------------------------------------------------------------------------------------------
   N-221        Client Cable Modem (single-user)                                     $495
----------------------------------------------------------------------------------------------
  N-221-S       Client Cable Modem (single-user), encryption support (DES)           $595
----------------------------------------------------------------------------------------------

<CAPTION>
COMMERICAL CABLE MODEM ACCESSORIES
<S>             <C>                                                         <C>
----------------------------------------------------------------------------------------------
  OTM-001       V.34 28.8 Phone Modem (typically US Robotics)                        $125
----------------------------------------------------------------------------------------------
  OEH-005       Ethernet Hub (5-port support for five computers)                      $80
----------------------------------------------------------------------------------------------
  CBL-001       RS-232 Modem Cable (see Note 5)                                       $8
----------------------------------------------------------------------------------------------

<CAPTION>
HYBRID TECHNICAL SUPPORT AND TRAINING
<S>             <C>                                                         <C>
----------------------------------------------------------------------------------------------
  TRN-201-4     One-Way Cable (640AM) Training Program                              $6,000
----------------------------------------------------------------------------------------------
  TRN-201-1     One-Way Cable (640AM) Training Program/Per Student                  $1,500
----------------------------------------------------------------------------------------------
  TRN-221-4     Two-Way Cable (640AM) Training Program                              $7,500
----------------------------------------------------------------------------------------------
  TRN-221-1     Two-Way Cable (640AM) Training Program/Per Student                  $1,875
----------------------------------------------------------------------------------------------
  TRN-240-4     Secure Router Training Program                                      $3,000
----------------------------------------------------------------------------------------------
  TRN-240-1     Secure Router Training Program/Per Student                           $750
----------------------------------------------------------------------------------------------
  SRV-100       System Integration per day                                          $1,500
----------------------------------------------------------------------------------------------
</TABLE>



                                                                       PAGE 18

<PAGE>

                                   ADDENDUM C

                              VOLUME DISCOUNT LEVELS

                            ALL PRICE IN U.S. DOLLARS

<TABLE>
<CAPTION>
                     MULTIPLE PC MODEM PRICES - TELEPHONE RETURN
                     -------------------------------------------
LEVEL          CABLE MODEM         QTY                      PRICE
-----          -----------         ---                      -----
<S>            <C>                 <C>                      <C>
1              CCM-201             0-1,000                  $795
2              CCM-201             1,001-3,000              $745
3              CCM-201             3,001-5,000              $695
4              CCM-201             5,001-10,000             $595
5              CCM-201             10,001-25,000            $570
6              CCM-201             25,001 AND GREATER       $540
NOTE:  for DES encryption add $100 per modem

<CAPTION>
                      SINGLE PC MODEM PRICES - TELEPHONE RETURN
                      -----------------------------------------
LEVEL          CABLE MODEM         QTY                      PRICE
-----          -----------         ---                      -----
<S>            <C>                 <C>                      <C>
1              N-201               0-1,000                  $440
2              N-201               1,001-3,000              $395
3              N-201               3,001-5,000              $375
4              N-201               5,001-10,000             $345
5              N-201               10,001-25,000            $320
6              N-201               25,001 AND GREATER       $295
NOTE:  - for internal phone modem add $50.00 per modem (future release)
       - for DES encryption add $100 per modem


<CAPTION>
                       MULTIPLE PC MODEM PRICES - CABLE RETURN
                      -----------------------------------------
LEVEL          CABLE MODEM         QTY                      PRICE
-----          -----------         ---                      -----
<S>            <C>                 <C>                      <C>
1              CCM-221             0-1,000                  $845
2              CCM-221             1,001-3,000              $795
3              CCM-221             3,001-5,000              $745
4              CCM-221             5,001-10,000             $645
5              CCM-221             10,001-25,000            $620
6              CCM-221             25,001 AND GREATER       $595
NOTE:  for DES encryption add $100 per modem


                                                                        PAGE 19
<PAGE>

<CAPTION>
                        SINGLE PC MODEM PRICES - CABLE RETURN
                        -------------------------------------
LEVEL          CABLE MODEM         QTY                      PRICE
-----          -----------         ---                      -----
<S>            <C>                 <C>                      <C>
1              N-221               0-1,000                  $495
2              N-221               1,001-3,000              $470
3              N-221               3,001-5,000              $440
4              N-221               5,001-10,000             $420
5              N-221               10,001-25,000            $370
6              N-221               25,001 AND GREATER       $345
NOTE:  - for internal phone modem add $50.00 per modem (future release)
       - for DES encryption add $100 per modem
</TABLE>

   * UPON THE EXECUTION OF THIS AGREEMENT, RCN WILL QUALIFYFOR THE LEVEL 6
     PRICING AS LONG AS RCN PROCUREMENTS REMAIN CONSISTENT WITH PURCHASE
                          PLAN OVER TERM HEREOF.













                                                                        PAGE 20

<PAGE>

                                  ADDENDUM D

                           SYSTEM & SOFTWARE SUPPORT

MEDIA WARRANTY

Hybrid Networks warrants that the media on which the Hybrid Networks product
is recorded will be free from defects in material and workmanship under
normal use and service for a period of 90 days from shipment.  Defective
media will be replaced through the Hybrid Networks RMA process.

INITIAL 180 DAY SYSTEM SUPPORT

Initial 180-day support for all head ends "launched", telephone support,
maintenance releases, enhancement releases, system monitoring, technical
bulletins, and access to the electronic bulletin board.

SOFTWARE SUPPORT

For each site initial software support period begins from the date of Hybrid
Networks shipment of the first application software purchase of a particular
product type for each site.

The support period also applies to all Hybrid Networks software and firmware
products containing application code.

For the duration of the contract, Hybrid will provide the following software
support:

Definitions

When used in this booklet:

     a.   "Site or Site Location" - refers to physical customer location usually
          associated with a single address, including the floors of a single
          building or adjoining buildings, and which has a single network
          administrative authority.

     b.   "Software" - refers to those computer program products, including
          Maintenance Releases, in object code form which the customer has
          licensed from Hybrid Networks.

     c.   "Maintenance Release" - refers to new version levels of software,
          periodically distributed for the purpose of correcting problems in
          previous releases.


                                                                         PAGE 21

<PAGE>

     d.   "Enhancement Release" - is defined as new versions of the product
          which include significant changes and/or additions to functionality.

Software Support coverage will be provided free of charge for the duration of
the contract and is renewable on an annual basis at a price of $1,000 per
CyberManager-TM- per month.  The coverage provides for telephone support
through the Hybrid Networks Support Center and for active software products;
maintenance releases and enhancement releases occurring during the contract
term.  All software support customers will receive all relevant Technical
Bulletins that are released during their contract term and access to the WWW
on-line support.

Telephone support will consist of access to the Hybrid Networks Solution
Center during the normal Hybrid Networks hours of coverage (6am - 5pm Pacific
Time, Monday through Friday, excluding Hybrid Networks observed holidays).
The support group will provide responses to software related issues such as
installations, configuration and problem solving.

Maintenance releases and enhancement releases occurring during the contract
period will be automatically sent to contract customers at no additional
charge. The release quantities will be shipped in the same manner as the
contract was purchased.  For example, single unit contracts will receive a
"one-for-one" update kit and site contracts will receive one master update
kit per site.  The classification of a given release as "maintenance" or
"enhancement" is solely at Hybrid Networks discretion.  Both types of releases
will be issued on standard media and will include all relevant technical
documentation.

New software that comprises a new product model, versus an enhancement of an
existing model, will require a separate software support agreement.  The
distinction between new product models and enhancements of existing models is
at Hybrid Networks' discretion.

For customers whose initial support or contract term has lapsed without
renewal, telephone support and new releases will be available on a
chargeable, per incident basis.  In general, these charges will amount to
substantially more than an annual support contract.  Those wishing to
initiate or reinstate their contract status must first be running the current
released software version prior to the effective date of the contract.  This
prerequisite may require the purchase of a maintenance or enhancement release.


                                                                         PAGE 22

<PAGE>

                                  ADDENDUM E

                       TROUBLE TICKET PROCESS & CLEARING

STEP 1:       SERVICE REQUEST (IR) PROCESS

   - Call placed to Hybrid Support Center (800)516-9315 or (408)342-4299
   - 7am - 6pm Pacific Time
   - Call Logged using Customer Severity Level
   - IR is created or updated normally
   - Escalating an IR is initiated by entering date and time
   - Current and pending status will be updated daily


STEP 2:       RETURN MATERIAL AUTHORIZATION (RMA) PROCESS

   - Call placed to Hybrid Support Center (800)516-9315 or (408)342-4299
   - 7am - 6pm Pacific Time
   - Customer Provide Information to Hybrid
   - Name, Company, address, and telephone number
   - Model and serial number of equipment
   - Detail statement giving the reason for replacement and/or repair (also
     sent with returned equipment)
   - Warranty returns will be repaired with a 10-business day turnaround
   - Products diagnosed by the Support Center as "our-of-the-box" failures, or
     which fail within the first 30 days of usage at the customer site, will
     generally be replaced by the next business day


                                                                         PAGE 23

<PAGE>

                                  ADDENDUM F

                             ESCALATION PROCEDURES

NET CPS ESCALATION PROCEDURE CHART:

<TABLE>
<CAPTION>

----------------------------------------------------------------------------------------------------------------------------
                                    1             2               3           Escalated       Escalated          Other
                                Emergency    Significant       Limited           by              to            Advisories
----------------------------------------------------------------------------------------------------------------------------
<S>                             <C>          <C>               <C>            <C>             <C>           <C>
                                                                                                                Dir Eng
Escalation level: I-                                                           Net Ops         Director       Dir/Net Ops
   Net Ops Tech                 TO + 4 hrs   TO + 8 hrs      TO + 5 days                                        Salesman
   Support Staff                                                                               Net Ops
                                                                            Tech. Support
                          --------------------------------------------------------------------------------------------------
                                TO + 48 hrs  TO + 96 hrs     TO + 14 days                                   Director Net Ops
   2 - Net Ops                                                                Director         Director      VP Operations
   Team/Operations                                                                                               VP Eng
                                                                               Net Ops           Eng.           VP Sales
                                                                                                                Salesman
                          --------------------------------------------------------------------------------------------------
   3 - Engineering              TO + 5 days  TO + 14 days    TO + 30 days        Eng             Exec
                                                                                 VP              Staff
                          --------------------------------------------------------------------------------------------------
   4 - Exec Staff               - Emergency meeting for decision and
                                  contingency planning                           n/a             n/a               n/a
                          --------------------------------------------------------------------------------------------------

</TABLE>

- Times indicated are total elapsed clock hours from initial call
- Times apply equally to domestic and international calls
- TO Times for Headquarters Technical Support Engineers include one hour
  telephone response time
- Action plan supersedes the time frames
- Times are flexible in that escalation can occur faster
- Net Ops owns the "problem" and escalation tracking
- Escalation table incidents are not limited to hardware and software bugs, but
  can include enhancements for marketing or quality issues for manufacturing
- Escalation for severity 1 & 2 which go past Net Ops level will be raised at
  the weekly bug status meeting
- Action plan supersedes the time frames


                                                                         PAGE 24

<PAGE>

                                  ADDENDUM G

                          ACCEPTANCE TEST PROCEDURES

ACCEPTANCE TEST PROCEDURES

SCOPE OF ACCEPTANCE TEST

This acceptance test is designed to determine the functional status of the
equipment which Hybrid Networks has proposed, trained and has assisted with
installation.  The test will demonstrate that the system meets requirements
as specified in the Hybrid Networks' specifications.  All findings of the
test will be reported to the customer upon completion of testing.

     CONNECTIVITY TEST:
     Customer will randomly select one (1) Client Cable Modem (CCM) on the
     Customer's network.  Workstation (PC with Windows 95 End Node) to System's
     network connectivity will be established and verified by a user's CCM being
     logged onto the network.

     PING TEST:
     Once the user is network attached, the Customer and Hybrid will conduct
     Ping testing.  See Windows 95 DOS Ping command listed below.

        LOCAL PING TEST:
        With the Ping command, you can send a ping request to the local CCM to
        verify that it is receiving information.  Enter the IP address of the
        CCM in the destination-list field.  From the Windows 95 DOS prompt enter
        "ping < CCM IP Address >".

        REMOTE PING TEST:
        With the Ping command, you can send a ping request to the Hybrid
        CyberManager to verify that it is receiving information.  Enter the IP
        address of the CyberManager in the destination-list field.  From the
        Windows 95 DOS prompt enter "ping < CyberManager IP Address >".  This
        step will verify the complete network operation of the Hybrid Networks'
        System and the CCM.

     CYBERMANAGER FTP TEST:
     Once the user is network attached, the Customer and Hybrid will conduct FTP
     testing.  Using Hybrid's CableTest, run the FTP test to the CyberManager.
     File transfer ability will be proven.

     WWW TEST: (OPTIONAL)
     Access the World Wide Web (WWW) using Microsoft Internet Explorer 3.0 (or
     better), Netscape, Mosaic or equivalent.  This test can only be performed
     if the Customer has provide an Internet Access which has been configured.


                                                                         PAGE 25

<PAGE>

TEST REPORT

     A complete test report detailing how the above tests were performed, the
     exact configuration of the network, and the results of the tests will be
     generated.  This test report will be presented to Customer at test
     completion.

NOTES

1.   Failure of Customer to accept or reject the Network within a period of
     thirty (30) days of notification of certification as provided for herein
     shall be deemed System Acceptance.

2.   If Customer uses any portion of the Hybrid System for production purposes,
     the System shall be deemed accepted by Customer.

3.   Windows 95 DOS Ping Command Syntax.


     ---------------------------------------------------------------------------
     WINDOWS 95 DOS PING COMMAND:

     C:\WINDOWS>ping

     Usage:  ping [-t] [-a] [-n count] [-l size] [-f] [-i TTL] [-v TOS]
                  [-r count] [-s count] [[-j host-list] | [-k host-list]]
                  [-w timeout] destination-list

     Options:
        -t             Ping the specified host until interrupted.
        -a             Resolve addresses to hostnames.
        -n count       Number of echo requests to send.
        -l size        Send buffer size.
        -f             Set Don't Fragment flag in packet.
        -i TTL         Time To Live.
        -v TOS         Type Of Service.
        -r count       Record route for count hops.
        -s count       Timestamp for count hops.
        -j host-list   Loose source route along host-list.
        -k host-list   Strict source route along host-list.
        -w timeout     Timeout in milliseconds to wait for each reply.
     ---------------------------------------------------------------------------



                                                                         PAGE 26

<PAGE>

                                 CERTIFICATION
                                      OF
                                  ACCEPTANCE


Customer Name: ____________________

Contract Number: __________________

Contract Date: ____________________

Site Location: ____________________

Scope of Work:

______________________________________________________

______________________________________________________

______________________________________________________

<TABLE>
<CAPTION>

--------------------------------------------------------------------------------
TEST                                                    COMPLETED
--------------------------------------------------------------------------------
<S>                                                     <C>
CONNECTIVITY TEST:                                            / /
--------------------------------------------------------------------------------
PING TEST:                                                    / /
--------------------------------------------------------------------------------
       LOCAL PING TEST:                                       / /
--------------------------------------------------------------------------------
       REMOTE PING TEST:                                      / /
--------------------------------------------------------------------------------
CYBERMANAGER FTP TEST:                                        / /
--------------------------------------------------------------------------------
WWW TEST: (Optional)                                          / /
--------------------------------------------------------------------------------
(Only if Internet Access is configured)
--------------------------------------------------------------------------------

</TABLE>

I hereby certify that the work represented by the contract described above
has been completed by Hybrid Networks and was given final inspection and
acceptance on _________________.

____________________________                        ____________________
Sign - Customer                                                   Date

____________________________
Print

____________________________                        ____________________
Sign - Hybrid Networks                                            Date

____________________________
Print


                                                                         PAGE 27

<PAGE>

                                  APPENDUM H

                              SYSTEM DESCRIPTION


See "Hybrid Series 2000 System Description" document number 018-00003-01


                                                                         PAGE 28