Document:

<PAGE>   1
                                                                     EXHIBIT 4.1

------                                                                ------
NUMBER                                                                SHARES
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                                    TELOCITY

              INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE
    THIS CERTIFICATE IS TRANSFERABLE IN NEW YORK, NY AND RIDGEFIELD PARK, NY

THIS CERTIFIES THAT:

IS THE RECORD HOLDER OF:

            FULLY PAID AND NON-ASSESSABLE SHARES OF COMMON STOCK, OF
  TELOCITY, INC., TRANSFERABLE ON THE BOOKS OF THE CORPORATION IN PERSON OR BY
  DULY AUTHORIZED ATTORNEY ON SURRENDER OF THIS CERTIFICATE PROPERLY ENDORSED.
 THIS CERTIFICATE SHALL NOT BE VALID UNTIL COUNTERSIGNED AND REGISTERED BY THE
TRANSFER AGENT AND REGISTRAR. WITNESS THE FACSIMILE SEAL OF THE CORPORATION AND
                THE SIGNATURES OF ITS DULY AUTHORIZED OFFICERS.

DATED:

                                                CHASEMELLON SHAREHOLDER SERVICES<PAGE>   1
                                                                   EXHIBIT 10.52

                  [INTERNATIONAL DATA CORPORATION LETTERHEAD]

                                                                  March 23, 2000

Telocity, Inc.
10355 North De Anza Boulevard
Cupertino, California 95014

     RE: CONCURRENCE WITH INFORMATION USED IN PROSPECTUS

To whom it may concern:

     We make reference to your request for concurrence with statements made in
Telocity's prospectus regarding statistics obtained from our company. Telocity
has filed a Registration Statement with the Securities Exchange Commission
(the "SEC") to register its shares for an initial public offering. You have
sought our concurrence with statements made in your prospectus regarding
statistics obtained from our Company.

     We hereby concur with the attached statements in Telocity's S-1 using
information obtained from our company.

                                        /s/ [SIGNATURE ILLEGIBLE]
                                        -------------------------
                                        Name:
                                        Title:
<PAGE>   2
                             Exhibit 10.52 (cont'd)

Page 35
According to IDC, from 1999 through 2003, the annual growth of U.S. households
with Internet access is projected to be 16%, with over 65 million users by the
end of 2003.

Page 36
IDC predicts that consumer purchases of goods and services over the Internet
will increase from $26 billion in 1999 to approximately $119 billion in 2003.

According to IDC, the total DSL capable access lines in the U.S. will grow from
an estimated 20.8 million in 1999 to 67.2 million in 2003.<PAGE>   1

                                                                    EXHIBIT 10.8

                                  CONFIDENTIAL

                        AGREEMENT ON TERMS AND CONDITIONS
                   OF PURCHASE AND SALE OF OPTICAL COMPONENTS

        This Agreement ("Agreement") is made as of this 1st day of January, 2000
by and between Corning Incorporated, a New York Corporation, with an address at
Houghton Park, Corning, NY 14831 ("Corning") and New Focus, Inc. with an address
at 2630 Walsh Avenue, Santa Clara, CA 95051 ("Seller").

        WHEREAS, Corning and certain of its affiliated companies plan to place
with Seller from time to time during the terms of this Agreement specific orders
for the purchase of certain Optical Components ("Materials"); and

        WHEREAS, the parties wish to provide for the general terms and
conditions upon which such Materials purchase transactions shall be made; and

        WHEREAS, the parties may wish to subsequently provide for certain
services for processing or additional goods and services related to the
Materials;

        NOW THEREFORE, in consideration of the mutual covenants herein, Corning
and Seller hereby agree as follows:

1.   Term. The Term of this Agreement shall be from January 1, 2000 through
     December 31, 2000 If the parties are not in breach at the expiration of the
     Term, then they may mutually agree in writing to continue this Agreement,
     upon thirty (30) days' notice prior to the term expiration date, for an
     additional one (1) year term.

2.   Scope. During the Term of this Agreement, the terms and conditions
     specified by this Agreement shall apply to all purchases of the Materials
     by Corning from Seller. This Agreement is based upon an anticipated
     procurement of Materials described in Appendix 1. The estimated quantity of
     each item of Materials to be purchased hereunder is described in the same
     Appendix. That estimated quantity for each item is based on an allocation
     to Seller of a share (expressed as a percentage) of Corning's purchases
     from unaffiliated companies of that item. Corning anticipates that this
     share allocation to the Seller will not change during the term of this
     Agreement provided the Seller can meet its delivery and other obligations
     under this Agreement, and can continuously keep Corning competitive in the
     market place. Corning may conduct business reviews with the Seller on a
     periodic basis (monthly, quarterly, semi-annually) to review the overall
     market situation and discuss changes needed to maintain a competitive
     position in the communications industry.

3.   Releases. When Corning wishes to purchase Materials pursuant to this
     Agreement, it shall submit a written release form for a specific quantity
     to Seller. Seller shall ship Materials in accordance with the Corning
     release. Release forms may be delivered to Seller via fax, email, EDI, or
     U.S. mail.

4.   Schedule and Safety Stock. Corning's schedules depend upon timely delivery
     of Materials and therefore, time is of the essence in Corning's release
     forms issued to Seller hereunder. Seller agrees to make timely delivery in
     accordance with agreed

<PAGE>   2

     upon delivery dates. In order to assure Corning of continuity of supply,
     Seller will keep as a safety stock a four-week supply of finished goods of
     each Material exclusively for Corning for which Corning shall be
     responsible to purchase upon termination or Material discontinuance.
     Corning will authorize and update, on a quarterly basis, the safety stock
     level required by product that the Seller will have available to ship. If
     this level exceeds four (4) weeks of the demand, Corning shall only be
     obligated to purchase the authorized four (4) weeks supply upon termination
     or material discontinuance.

5.   Price(s) and Quantity. During the Term, the guaranteed prices, and
     estimated quantities of the Materials sold by Seller to Corning shall be as
     specified in Appendix I hereto.

6.   Delivery. Unless otherwise agreed, all price and delivery terms shall be on
     a delivered basis, broken out specifying price, insurance, and freight
     separately.

7.   Performance. Corning will provide a minimum of 3 weeks lead time on new
     purchase orders and 2 weeks lead time on schedule changes on forecasts.

     Corning will provide at least a three (3) month or greater rolling Forecast
     reflecting, by time period, shipping quantities required for each part
     number to support Corning's manufacturing schedules.

     Seller agrees to make timely deliveries in accordance with agreed upon
     delivery dates.

8.   Title. Title to and possession of all Materials shipped by Seller to
     Corning shall pass to Corning upon delivery of materials at the Corning
     location.

9.   Warranty/Specifications. At the time of delivery, Seller warrants that
     title to the Materials shall pass to Corning, free and clear of claims or
     liens of third parties. Seller also warrants that the Materials supplied by
     Seller to Corning hereunder shall meet the quality levels and specification
     levels defined in Appendix II. Materials shall be free of objects or other
     substances which, in the opinion of Corning, could render them until for
     intended use. If quality levels are not defined in Appendix II for a
     particular item, then Seller warrants that such Materials shall be
     merchantable, of best quality and free from defects in materials,
     processing or workmanship. This warranty shall survive any inspection by
     Corning.

     Any attempt by Seller to limit, disclaim, or restrict any such warranties
     or any remedies of Corning, by acknowledgment or otherwise, in accepting or
     performing this order, shall be null, void and ineffective without
     Corning's written consent.

     The initial warranty period of Materials shipped under the terms and
     conditions of this Agreement will be [*] from the date of shipment by
     Supplier. Any purchased device which is rejected for non-conformance to
     Corning's specification will be returned to Seller. Seller will, at
     Corning's option and without limiting any other rights of Corning, either:
     (1) credit Corning the value of device, (2) replace the device at no
     expense to Corning, or (3) repair the device at no cost to Corning.

10.  Software & Systems Warranty. Seller warrants that the quality and delivery
     of the Material will not be affected by any computer system and/or software
     related

[*] Certain information on this page has been omitted and
    filed separately with the Commission. Confidential treatment
    has been requested with respect to the omitted portions.
<PAGE>   3

     malfunction including, but not limited to, changes in dates, the passing of
     the calendar years 1999 or 2000, the next millennium and/or leap years.
     Should Seller fail to meet the requirements of this Agreement due to such
     computer system and/or software related malfunctions, Corning may (without
     prejudice to any other available remedy or cause of action) terminate this
     Agreement on five (5) days advance written notice to Seller. Additionally,
     Corning may terminate this Agreement if Seller, when requested, fails to
     give adequate assurance that it or any of its suppliers are Year 2000
     compliant.

11.  Inspection. Corning shall be entitled to inspect Materials upon delivery.
     Any prior inspection of Materials or sampling at the Seller's facility by
     Corning personnel will imply neither delivery or acceptance of such
     Materials by Corning.

12.  Plant Access. Seller will allow representatives of Corning and Corning's
     customers access to the facilities involved in performing this order for
     purposes of reviewing the status and progress of production and witnessing
     any test and inspections. Such access will not relieve Seller of any of its
     obligations.

13.  Inspection Reports. Seller shall furnish Corning with Inspection Reports
     for each shipment of Materials hereunder. Seller shall collect all relevant
     data for each Material prior to shipment. Such Certificates of Analysis
     shall be specific by traceable notations and Corning may reject items that
     do not meet the specifications in Appendix II. Inspection reports shall
     accompany all Materials shipped to Corning. Duplicate copies shall be filed
     and stored by Seller for a period of seven (7) years in case future
     reference is required by Corning.

14.  Invoicing and Payment. Seller shall invoice Corning in duplicate for
     Materials ordered by and delivered to Corning. Corning shall pay such
     invoices within forty-five (45) days after their receipt. Corning shall not
     be required to pay invoices for any Materials which do not meet applicable
     specifications or for quantities other than those it ordered.

15.  Process Changes. Seller shall notify Corning in writing and at least 30
     days in advance of any change in its manufacturing, assurance of supply,
     refining, feedstock, process or equipment that might affect Corning's
     results, its access to, or its use of the Materials purchased from Seller
     hereunder.

16.  Design Changes. In the event that Corning's requirements for Materials
     change, Corning and Seller shall meet in good faith to discuss possible
     changes in the design of Materials and may amend the specifications to
     comply with Corning's new requirements. If Seller has the technical
     capability to meet Corning's new requirements, Seller shall do so. Any
     price adjustments resulting from proposed design changes will be negotiated
     in godd faith by Seller and Corning.

17.  Patents. Seller agrees to indemnify, hold harmless and protect Corning
     against any costs (including reasonable attorneys' fees), liabilities, and
     judgments arising from any claim made by a third party against Corning that
     the materials supplied by Seller under this Agreement infringe patent or
     copyrights of such third party. Corning shall promptly notify Seller of any
     such claim, agrees to provide information and reasonable assistance, and
     give Seller sole authority to defend or settle such claim. Upon notice of
     an alleged infringement, Seller may, at its option and expense, (i) obtain
     for Coming the right to continue using the Materials, (ii) replace or
     modify the product so that is

<PAGE>   4

     becomes non-infringing or non-violating, (iii) substitute an equivalent
     non-infringing version of the Materials. In the event that none of the
     above options is reasonably available, either party may terminate this
     Agreement and Corning may return any and all Materials paid for and in
     Corning's inventory and obtain a refund from Seller of the price paid by
     Corning for such inventory. Termination hereunder does not discharge the
     obligations of Seller to defend Corning and pay costs or judgments.

     Notwithstanding the above provisions, Seller assumes no liability for any
     infringement claims based upon the use of the Materials either (i) in
     connection or in combination with equipment, devices, products or software
     not provided by Seller if such claims would not have resulted but for some
     combination or use, or (ii) for other than normal purposes.

     THE FOREGOING STATES EACH PARTY'S SOLE AND EXCLUSIVE REMEDY WITH RESPECT TO
     CLAIMS OF INFRINGEMENT OR VIOLATION OF THIRD PARTY PROPRIETARY RIGHTS OF
     ANY KIND.

18.  Excusable Failure or Delay (Force Majeure). Neither party shall be held
     responsible for the failure or delay in performance hereunder where such
     failure or delay is due to any act of God or of the public enemy, war,
     compliance with laws, governmental acts or regulations, fire, flood,
     epidemic, accident, unusually severe weather or other causes similar to the
     foregoing beyond their reasonable control. Any party whose performance is
     affected by such force majeure shall promptly give notice to the other
     party of the occurrence or circumstance upon which it intends to rely to
     excuse its performance. If the circumstances of force majeure affecting
     either party's performance hereunder delays performance for more than seven
     (7) days, then the other party may terminate this Agreement upon seven (7)
     days' advance written notice. In no event shall a failure or delay in
     performance attributable to the "Year 2000" or other computer system and/or
     software related malfunction be excusable under this paragraph or any other
     paragraph of this Agreement.

19.  [*]

20.  Price Protection. If Corning submits substantial evidence in writing that
     another producer of goods has lawfully offered Corning goods of similar
     quality, in similar quantities and under like terms and conditions, at a
     delivered cost at least [*] lower than the delivered cost hereunder, then
     Corning will give Seller written notice of such lower offer.

[*] Certain information on this page has been omitted and
    filed separately with the Commission. Confidential treatment
    has been requested with respect to the omitted portions.
<PAGE>   5

     If Seller does not agree, in writing and within thirty (30) days of such
     notice, to reduce its price immediately to meet that lower offer, then, at
     the expiration of that thirty (30) day period, Corning's only purchase
     obligation hereunder will be to purchase Materials for which releases have
     already been issued by Corning and accepted by Seller. Upon the purchase by
     Corning of the Materials under those prior releases, Corning will be deemed
     to have satisfied any and all purchase commitments and obligations
     hereunder, and will not be subject to any penalty, price adjustment or
     other liability for failure to purchase any additional Materials from
     Seller.

21.  No Assignment. This Agreement shall not be assigned and is not assignable
     or delegable by either party without the written consent of the other,
     which shall not be unreasonably withheld.

22.  Compliance with Laws. Seller shall comply with all applicable federal,
     state and local laws and regulations in the manufacture, processing, sale
     and transport of the Materials to be delivered hereunder. In the event that
     Seller's work does not comply with any such laws, codes, and regulations,
     Seller shall correct any such noncompliance at its sole expense and
     indemnify and hold Corning harmless from any claims, costs, fines,
     penalties, expenses, liabilities or losses on account of any such
     noncompliance.

23.  Default and Termination. This Agreement and all rights granted hereunder
     may be terminated by either party: (a) in the event of a continuing default
     by the other party of any obligation hereunder, effective seven Corning
     business (7) days after written notice of such default is given to the
     defaulting party; or (b) immediately in the event that either a delivery
     that is more than fifteen (15) Corning business days late, or if any three
     (3) deliveries are more than seven (7) Corning business days late in any
     six-month period; or (c) immediately upon written notice in the event of
     bankruptcy, insolvency or any other financial condition creating reasonable
     doubt as to that party's ability to perform hereunder. If any instance
     under (a) or (b) occur, Corning must notify Seller in writing within (30)
     days of each event. In the event that Corning does not notify Seller,
     termination rights for that event lapse.

     No such termination shall affect or discharge any obligations of either
     party which arose prior to the effective date of termination with respect
     to warranties, indemnification, moneys owed or confidential information.

24.  Cancellation for Buyer's Convenience. Corning may cancel a firm Purchase
     Order at any time prior to delivery. In the event of such cancellation,
     Seller shall immediately cease to incur expense against the affected
     Purchase Order.

     If the purchase order covered standard product which is easily sellable to
     Seller's other customers, the Corning will have no liability to Seller for
     cancellation of the Purchase Order.

     For Purchase Orders for nonstandard products, Corning's liability in the
     event of cancellation shall be limited to the following for deliveries
     cancelled under such Purchase Order:

<PAGE>   6

        a. Actual cost incurred by Seller, up to and including the date of
           cancellation for material costs and direct labor costs; and

        b. Reasonable costs that Seller has reasonably committed to pay to its
           suppliers; and for the materials for undelivered quantities.

     Seller shall use reasonable endeavors to mitigate the amount of such
     charges. Seller will provide Corning with clear documentation of all costs
     and charges which Corning is liable under this provision. In no event will
     Corning be liable for cancellation charges in excess of the contract value
     of the Materials cancelled. Upon payment of such cancellation charges by
     Corning, Seller shall deliver to Corning, in accordance with the delivery
     terms of this Agreement, all work in progress and inventory for which
     Corning has made payment.

25.  Obsolescent. Corning reserves the right to reduce estimated quantities (but
     maintaining share percentage) or substitute new products for those
     referenced in Appendix I, in the event that new products offering a
     superior technological or economic advantage become available during the
     term of this Agreement. Seller shall be given a reasonable amount of time
     to match such new products.

26.  Waiver. The failure of Corning to insist in any one or more instances upon
     the full performance of any of the terms, covenants or conditions of this
     order or to exercise any rights it may have hereunder shall not be
     construed as a waiver of any legal rights it may have with respect to such
     nonperformance or be construed as Corning's condoning further
     nonperformance of such terms, covenants or conditions.

27.  Confidential Information. The nondisclosure agreement entered into by the
     Parties on March 15, 1999 will govern the use of confidential information
     by Seller. The term of the nondisclosure agreement will be the term of this
     Agreement. This Agreement and its terms are subject to that nondisclosure
     agreement.

28.  Promotion Limitation: Seller agrees that it will not use Corning's name
     whether by including reference to Corning in any list of customers
     advertising that its services or products are used by Corning or otherwise,
     without written authorization by Corning's authorized representative.

29.  Liability. To the fullest extent permitted by law, Seller hereby
     indemnifies and agrees to hold harmless Corning, its affiliates,
     subsidiaries, agents, employees, directors, or representatives from and
     against all claims, damages, losses and expenses, including but not limited
     to attorneys' fees, arising out of or resulting from Seller's supply of
     Materials or performance of these services.

30.  Insurance. If Seller performs any services for Corning on Corning's
     premises, Seller shall, at any time(s) upon request, furnish Corning with
     an insurance certificate(s) from its insurance carrier(s) naming Corning as
     an additional insured, evidencing the existence of insurance coverage of
     the following kinds in at least the following amounts:

        A. Workers' compensation insurance as required by law and Employer's
           liability insurance with limits not less than One Million Dollars
           ($1,000,000).

<PAGE>   7

        B. Comprehensive public liability insurance for personal injury
           (including death) and property damage with limits of not less than
           Five Million Dollars ($5,000,000) for personal injury and property
           damage, including coverage for owned and nonowned automobiles and
           Seller's contractual obligations.

        C. Umbrella liability insurance with limits not less than Five Million
           Dollars ($5,000,000).

31.  Choice of Law and Forum. This Agreement shall be governed by, interpreted
     and construed and performance hereunder shall be determined in accordance
     with the law of the State of New York, without regard to its conflicts of
     law principles. In the event of disputes or claims relating to this
     Agreement, both parties agree to seek an amicable settlement prior to
     commencing any litigation. In the event of litigation, any action shall be
     venued in either the Supreme Court of the State of New York, Steuben
     County, or in the United States District Court, Western District of New
     York.

32.  Conflict of Terms. The terms and conditions of Corning stated on this
     Agreement shall govern in the event of any conflict with any terms proposed
     by Seller, and are not subject to change by reason of any written or oral
     statements by Seller or by any terms stated in Seller's acknowledgement of
     this order, unless such conflicting or additional terms are accepted in a
     writing making reference to this Agreement and signed by Corning. Shipment
     of goods or materials, or performance of services pursuant to this order
     shall be deemed to be an unqualified acceptance of the terms and conditions
     contained herein.

33.  Counterparts. This Agreement may be executed simultaneously in two or more
     counterparts, each of which shall be deemed an original, but all of which
     together shall constitute one and the same instrument.

34.  Notices, Entire Agreement and Change Orders. All notices delivered or
     demands given by either party under this Agreement shall be delivered in
     person, or forwarded by U.S. Mail, postage prepaid, or they may be faxed
     properly addressed to the authorized representatives of the party. This
     Agreement constitutes the entire agreement between Corning and Seller with
     respect to the Work, and supersedes all prior and contemporaneous
     negotiations, agreements, representations, understandings and commitments.
     No change, modification or extension of this Agreement shall be effective
     unless it is made in writing, makes specific reference to this Agreement
     and signed by duly authorized representatives of Corning and Seller. Such
     approval shall not be unreasonably withheld. For the purposes of this
     Agreement, the following persons are the authorized representatives of
     Buyer and Corning:

     For Corning:   Kathryn M. Murphy, Division Vice President,
                    Materials Management

     For Seller:    Paul G. Smith, Vice President and General Manager

35.  Ownership of Tools and Intellectual Property. Corning shall have title to
     and the right of immediate possession of any tools, equipment or prototypes
     furnished or paid for by Corning, and if and when any such Corning property
     is in the possession of Seller,

<PAGE>   8

     Seller shall not use such property for any work other than that of Corning
     and shall maintain such property in good and usable condition at no further
     cost to Corning.

     Pursuant to the terms of the confidentiality agreement between Corning and
     Seller, Seller will not use any confidential information of Coming (as
     defined in that agreement) for any purpose other than the supply of
     Materials to Corning. Accordingly, if Seller uses any such confidential
     information of Corning to design or make any Materials, then those
     Materials will be sold only to Corning and Seller will not sell or offer to
     sell those Materials to any third party without the prior written consent
     of Corning.

     IN WITNESS WHEREOF, Seller and Corning have executed this Agreement by
     their respective duly authorized representatives as of the date first above
     written.

     SUPPLIER NAME                          CORNING INCORPORATED

     By: /s/ PAUL SMITH                     By: /s/ KATHRYN M. MURPHY
        --------------------------------        --------------------------------
                                                    Kathryn M. Murphy

     Title: VP/GM Telecom Division          Title: Division Vice President,
                                                   Materials Management

     Date: 2/18/00                          Date: 2/14/00

<PAGE>   9

                                   APPENDIX I

                              Quantity and Pricing

1.   Quantity. Corning will purchase from New Focus a percentage (listed below
     in Share) of its external requirements of the Materials during the term of
     this Agreement. The forecasted volumes below are an estimate to be used for
     the Seller's information purposes only, and is not intended to bind or
     obligate Corning to purchase said amount.

2.   Pricing.

<TABLE>
<CAPTION>
     Product                 Share      Est Volume    Price (1/1-6/30)*    Price (7/1-12/31)*
     -----------------       -----      ----------    -----------------    ------------------
<S>                          <C>        <C>           <C>                  <C>
     [*]
</TABLE>

     All pricing takes effect 1/1/00. Any current purchase orders will
     cancelled 12/30/99 and new purchase orders placed at the new pricing.

[*] Certain information on this page has been omitted and
    filed separately with the Commission. Confidential treatment
    has been requested with respect to the omitted portions.
<PAGE>   10

                                   APPENDIX II

                             PURCHASE SPECIFICATION

<TABLE>
<CAPTION>
                                                             CORNING SPEC
CORNING PART NUMBER            DESCRIPTION                   NUMBER/DATE
-------------------            -----------                   ------------
<S>                            <C>                           <C>
[*]
</TABLE>

     This product shall be free from all other material or objects which, in the
     opinion of Corning Incorporated, could render it unfit for its intended
     use.

     All measurements made to determine compliance with this specification shall
     be done in accordance with analytical procedures approved by Corning
     Incorporated.

[*] Certain information on this page has been omitted and
    filed separately with the Commission. Confidential treatment
    has been requested with respect to the omitted portions.

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