Exhibit 4.10  SPIRENT
plc   
  THIRD
AMENDMENT, CONSENT AND  WAIVER
AGREEMENT  
   DATED
MARCH 1, 2005   US$10,000,000
AMENDED AND RESTATED SERIES A SENIOR NOTES DUE NOVEMBER 23, 2006  US$63,406,000
AMENDED AND RESTATED SERIES B SENIOR NOTES DUE NOVEMBER 23, 2009  US$115,000,000
AMENDED AND RESTATED SERIES C SENIOR NOTES DUE NOVEMBER 23, 2009  US$29,594,000
AMENDED AND RESTATED SERIES D SENIOR NOTES DUE NOVEMBER 23, 2009   BINGHAM
MCCUTCHEN LLP
LONDON


SPIRENT
plc  
  THIRD
AMENDMENT, CONSENT AND  WAIVER
AGREEMENT  
  US$10,000,000
AMENDED AND RESTATED SERIES A SENIOR NOTES DUE NOVEMBER 23, 2006  US$63,406,000
AMENDED AND RESTATED SERIES B SENIOR NOTES DUE NOVEMBER 23, 2009  US$115,000,000
AMENDED AND RESTATED SERIES C SENIOR NOTES DUE NOVEMBER 23, 2009  US$29,594,000
AMENDED AND RESTATED SERIES D SENIOR NOTES DUE NOVEMBER 23, 2009   Dated March 1, 2005  To each of the Current Noteholders
Named in Annex 1 hereto:  Ladies and Gentlemen:  SPIRENT plc,
a limited company organized and existing under the laws of England and Wales
with registered number 470893 (together with its successors and assigns, the Company), hereby
agrees with you as follows:  1.PRIOR
ISSUANCE OF NOTES, ETC.  Pursuant to the separate Note Purchase
Agreements, dated November 23, 1999, among the Company (formerly known as
Bowthorpe plc) and, respectively, the purchasers named in Schedule A
thereto (as amended and restated pursuant to the Amended and Restated Note
Purchase Agreement dated March 11, 2003 and as further amended pursuant to
the Amendment and Consent Agreement dated December 31, 2003 and the Second
Amendment and Consent Agreement dated August 13, 2004, and as in effect
immediately prior to giving effect to the Amendments (defined below) provided
for by this Agreement, collectively, the Existing Note Purchase Agreement, and as
may be amended pursuant to the Amendments or further amended, restated or
otherwise modified from time to time, collectively, the Note Purchase Agreement),
the Company issued and sold (a) US$10,000,000 aggregate original principal
amount of its Amended and Restated Series A Senior Notes due November 23,
2006, (b) US$63,406,000 aggregate original principal amount of its Amended
and Restated Series B Senior Notes due November 23, 2009,


(c) US$115,000,000 aggregate original principal amount of its
Amended and Restated Series C Senior Notes due November 23, 2009, and
(d) US$29,594,000 aggregate original principal amount of its Amended and
Restated Series D Notes due November 23, 2009 (as in effect immediately
prior to the Effective Time (as defined below), the Existing Notes and,
as may be amended pursuant to the Amendments or further amended, restated or
otherwise modified from time to time, the Notes).  This Third Amendment, Consent and Waiver
Agreement is referred to herein as this Agreement. 
The register kept by the Company for the registration and transfer of
the Notes indicates that each of the Persons named in Annex 1 (collectively,
the Current Noteholders)
is currently a holder of the Notes in the aggregate principal amount indicated
opposite such Persons name in such Annex and that the Persons named in Annex 1
currently hold 100% of the outstanding Notes.  2.DEFINED
TERMS.  Capitalized terms used herein and not
otherwise defined have the meanings ascribed to them in the Existing Note
Purchase Agreement.  3.REQUEST
FOR CONSENT.  The Company requests that each of you consent
to the Amendments with respect to certain terms of the Existing Note Purchase
Agreement and to certain other matters specified in this Agreement.  4.COMPANY
WARRANTIES AND REPRESENTATIONS.  To induce you to enter into this Agreement,
the Company warrants and represents as follows (it being agreed, however, that
nothing in this Section 4 shall affect any of the warranties and
representations previously made by the Company in or pursuant to the Note
Purchase Agreement and that all of such other warranties and representations,
as well as the warranties and representations in this Section 4, shall
survive the effectiveness of the Amendments and the Waiver):  4.1Corporate Organization
and Authority.  (a)The
Company and each of its Material Subsidiaries is a corporation or other legal
entity duly organized, validly existing and, in the case of each such Material
Subsidiary organized under the laws of any state of the United States of
America, in good standing under the laws of its jurisdiction of incorporation.  (b)The
Company and each of its Material Subsidiaries has the corporate or other power
and authority to own or hold under lease the properties it purports to own or
hold under lease, to transact its business as now conducted and as presently
proposed to be conducted.  (c)The
Company and each of its Material Subsidiaries is duly qualified and, in the
case of each such Material Subsidiary conducting business in any state of the
United States of America, is in good standing as a foreign corporation in each
jurisdiction wherein the nature of the business transacted by it, or the nature
of the property owned or leased by it, makes such qualification required by law
and where  3


failure to be so
qualified or in good standing would, individually or in the aggregate,
reasonably be expected to have a Material Adverse Effect on the business,
operations or financial condition of the Company and its Subsidiaries, taken as
a whole.  4.2Financial Indebtedness.  The Financial
Indebtedness of the Company and its Subsidiaries as at December 31, 2004
is described in Part 4.2 of Annex 2.  4.3Agreements Authorized;
Obligations Enforceable.  (a)The
execution and delivery by the Company of this Agreement has been duly
authorized by all necessary corporate action on its part.  This Agreement has been executed and
delivered by one or more duly authorized officers or directors of the Company,
and each of this Agreement, the Notes and the Note Purchase Agreement, after
giving effect to the Amendments and the Waiver, constitute a legal, valid and
binding obligation of the Company, enforceable in accordance with its terms,
except that the enforceability hereof and thereof may be limited by:  (i)applicable bankruptcy, reorganization, arrangement,
insolvency, moratorium, or other similar laws affecting the enforceability of
creditors rights generally; and  (ii)general principles of equity (regardless of whether
enforcement is sought in a proceeding in equity or at law).  (b)The
execution and delivery by the Guarantors of the Acknowledgement and Consent
attached hereto has been duly authorized by all necessary action on the part of
each Guarantor.  The Acknowledgement and
Consent attached hereto has been executed and delivered by one or more duly
authorized officers or directors of each Guarantor, and the Subsidiary
Guarantees, after giving effect to the Amendments and the Waiver, will
constitute a legal, valid and binding obligation of each Guarantor in respect
thereof, enforceable in accordance with their terms, except that the
enforceability hereof and thereof may be limited by:  (i)applicable bankruptcy, reorganization, arrangement,
insolvency, moratorium, or other similar laws affecting the enforceability of
creditors rights generally; and  (ii)general principles of equity (regardless of whether
enforcement is sought in a proceeding in equity or at law).  4.4No Conflicts.  Neither the
execution nor delivery of this Agreement, nor performance by the Company with
the terms and provisions of the Notes or the Note Purchase Agreement, after
giving effect to the Amendments and the Waiver, nor compliance by each
Guarantor with the terms and provisions of its respective Subsidiary Guarantee,
will conflict with, or result in a breach of the terms, conditions or
provisions of, or constitute a default under, or result in any violation of, or
result in the creation of any Lien upon any of the properties of the Company or
any of its Subsidiaries under the  4


memorandum or articles of association (or
charter or by-laws) of the Company or any of its Subsidiaries, or any award of
any arbitrator or any agreement, instrument, order, judgment, decree, statute,
law, rule or regulation to which the Company or any of its Subsidiaries is
subject (including, without limitation, the 2005 Bank Facility (defined below)
and any agreement with shareholders).  4.5Full Disclosure.  Neither this
Agreement nor any other written statement furnished by or on behalf of the
Company or any of its Subsidiaries to the Current Noteholders in connection
with the proposal and negotiation of the Amendments and the Waiver, or the
other terms and provisions of this Agreement, contains any untrue statement of
a material fact or omits a material fact necessary to make the statements
contained therein, taken as a whole, under the circumstances under which made,
not misleading.  Except as previously
disclosed in writing to each Current Noteholder, there is no fact known to the
Company or any Material Subsidiary that could reasonably be expected to have a
Material Adverse Effect upon the business, operations or principal properties
of the Company and its Subsidiaries taken as a whole.  4.6Amendments to 2005 Bank
Facility.  There have been no amendments, waivers or other modifications to the
new credit facility dated February 2, 2005 which replaces the New Bank
Facility (as defined in the Amendment and Consent Agreement dated December 31,
2003) and provides for total commitments or borrowing availability in an
aggregate amount of at least £30,000,000 (the2005 Bank Facility) subsequent to February 2,
2005, and the 2005 Bank Facility is in full force and effect on the date
hereof.  4.7No Defaults.  After giving
effect to the Waiver provided in Section 6, no Default or Event of Default
has occurred and is continuing.  No event
has occurred and no condition exists that would constitute a default, event of
default or potential default (howsoever described) under the 2005 Bank
Facility.  4.8Guaranties.  No Subsidiary
of the Company, other than Subsidiaries which are Guarantors as at the
Effective Time, has entered into or is liable under any guaranty of any
Financial Indebtedness of any Person arising under the 2005 Bank Facility.  5.AMENDMENTS TO EXISTING NOTE PURCHASE
AGREEMENT.  Subject to the conditions specified in Section 7,
the Existing Note Purchase Agreement is hereby amended in the manner provided
in Exhibit A to this Agreement (the Amendments).  6.WAIVER.  Subject to the conditions specified in Section 7,
each Noteholder party hereto hereby waives (the Waiver), from the date of this Agreement,
the Event of Default constituted by the breach by the Company of the provision
of the letter agreement dated February 18, 2004  5


between the
Company and the Current Noteholders attached hereto as Annex 3 requiring the
Company to extend or refinance the New Bank Facility prior to January 30,
2005 (the existence of which Event of Default the Company hereby acknowledges
and confirms). The Company acknowledges and confirms that the Current
Noteholders do not confirm or waive, and fully reserve all their rights with
respect to, any other Default or Event of Default that may have occurred or may
occur.  7.CONDITIONS
TO EFFECTIVENESS.  The Amendments and the Waiver shall each
become effective, if at all, at such time (the Effective Time) as the Company and the
Required Holders shall have executed and delivered counterparts of this
Agreement and the following conditions shall have been satisfied by the Company
(or waived by the Required Holders):  7.1Representations and
Warranties.  The representations and warranties set forth
in Section 4 shall be true and correct.  7.2Due Authorization, etc.  The Company
shall have authorized, by all necessary corporate action, the execution and
delivery of this Agreement, the performance of all of its obligations under
this Agreement, and the consummation of all transactions by it contemplated by
this Agreement, and each Guarantor shall have authorized, by all necessary
corporate action, the execution and delivery of the Acknowledgement and Consent
attached hereto, and the Current Noteholders and their special counsel shall
have received such certificates and other evidence to such effect (including,
without limitation, secretarys certificates and board resolutions) as the Required
Holders and their special counsel may reasonably request.  7.3Fees and Expenses.  The Company shall have paid all amounts required to have been paid to
date pursuant to Section 8, including, without limitation, the reasonable
fees and expenses of Bingham McCutchen LLP, special counsel for the holders of
the Notes, and PricewaterhouseCoopers LLP, reporting accountants to the holders
of the Notes, as reflected in statements to be presented to the Company before
the Effective Time.  7.4Consent of Guarantors.  Each Guarantor
shall have indicated its acknowledgement and consent in respect of this
Agreement by executing and delivering the Acknowledgement and Consent attached
hereto.  8.EXPENSES.  Whether or not the Amendments and/or the
Waiver become effective, the Company will promptly (and in any event within
thirty (30) days of receiving any statement or invoice therefor) pay all
reasonable out-of-pocket costs and expenses of the Current Noteholders relating
to this Agreement and all related documentation contemplated herein, including,
but not limited to, (a) the cost of reproducing this Agreement and any
other documents delivered in connection herewith and the transactions
contemplated hereby, and (b) the reasonable fees  6


and expenses of
Bingham McCutchen LLP, special counsel for the holders of the Notes, and
PricewaterhouseCoopers LLP, reporting accountants to the holders of the Notes,
incurred in connection with such matters.  9.MISCELLANEOUS.  9.1Part of Note
Purchase Agreement, Future References, etc.  This Agreement
shall be construed in connection with and as a part of the Notes and the Note
Purchase Agreement and, except as expressly amended by this Agreement, all
terms, conditions and covenants contained in the Notes, the Note Purchase
Agreement and the Subsidiary Guarantees are hereby ratified and shall be and
remain in full force and effect.  Any and
all notices, requests, certificates and other instruments executed and
delivered after the execution and delivery of this Agreement may refer to the
Notes and the Note Purchase Agreement without making specific reference to this
Agreement, but nevertheless all such references shall include this Agreement
unless the context otherwise requires.  9.2Governing Law.  THIS
AGREEMENT SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE WITH, AND THE RIGHTS OF
THE PARTIES SHALL BE GOVERNED BY, THE LAW OF THE STATE OF NEW YORK EXCLUDING
CHOICE-OF-LAW PRINCIPLES OF THE LAW OF SUCH STATE THAT WOULD REQUIRE THE APPLICATION
OF THE LAWS OF A JURISDICTION OTHER THAN SUCH STATE.  9.3Duplicate Originals,
Execution in Counterpart.  Two (2) or
more duplicate originals hereof may be signed by the parties, each of which
shall be an original but all of which together shall constitute one and the
same instrument.  This Agreement may be
executed in one or more counterparts and shall be effective at the time
provided in Section 7 and each set of counterparts that, collectively,
show execution by the Company and each consenting Current Noteholder shall
constitute one duplicate original.   [signature pages immediately follow]  7


If this Agreement is satisfactory to you,
please so indicate by signing the applicable acceptance on a counterpart hereof
and returning such counterpart to the Company.  Very truly yours,SPIRENT plcByName:Title:   [Signature
page for THIRD AMENDMENT, CONSENT AND WAIVER AGREEMENT of SPIRENT PLC]


THE LINCOLN NATIONAL LIFE INSURANCE COMPANY By:
  
  Delaware Investment Advisers, a Series of
  DelawareManagement Business Trust, Its
  Attorney-in-Fact   ByName:Title:


LINCOLN LIFE & ANNUITY COMPANY OF
NEW YORK By:
  
  Delaware Investment Advisers, a Series of
  DelawareManagement Business Trust, Its
  Attorney-in-Fact   ByName:Title:


FIRST PENN-PACIFIC LIFE INSURANCE COMPANY By:
  
  Delaware Investment Advisers, a Series of
  DelawareManagement Business Trust, Its
  Attorney-in-Fact   ByName:Title:


METROPOLITAN LIFE INSURANCE COMPANY   ByName:Title:


METROPOLITAN PROPERTY AND CASUALTY INSURANCE COMPANY By:
  
  Metropolitan Life Insurance CompanyIts Investment Manager   ByName:Title:


METROPOLITAN TOWER LIFE INSURANCE COMPANY By:
  
  Metropolitan Life Insurance CompanyIts Investment Manager   ByName:Title:


TEACHERS INSURANCE AND ANNUITY ASSOCIATION OF AMERICA   ByName:Title:


THE TRAVELERS INSURANCE COMPANY   ByName:Title:


PRIMERICA LIFE INSURANCE COMPANY   ByName:Title:


CONNECTICUT GENERAL LIFE INSURANCE COMPANY By:
  
  CIGNA Investments, Inc. (authorized
  agent)   ByName:Title:


LIFE INSURANCE COMPANY OF NORTH AMERICA By:
  
  CIGNA Investments, Inc. (authorized
  agent)   ByName:Title:


MASSACHUSETTS MUTUAL LIFE INSURANCE COMPANY By:
  
  Babson Capital Management LLC asIts Investment Adviser   ByName:Title:


SWISS RE LIFE & HEALTH AMERICA INC By:
  
  Swiss Re Asset Management (Americas) Inc.   ByName:Title:


ACKNOWLEDGEMENT
AND CONSENT  Each of the undersigned hereby acknowledges, consents and agrees to the
terms and provisions of this Agreement and confirms that its Subsidiary
Guarantee continues in full force and effect in respect of the Notes and the
Note Purchase Agreement as amended by the Amendment and Consent Agreement dated
December 31, 2003, the Second Amendment and Consent Agreement dated August 13,
2004 and by the terms of this Agreement.  EXECUTED
by PG DRIVES TECHNOLOGY,
INC.  By:Name:Title:   EXECUTED
by SPIRENT
COMMUNICATIONS INC.  By:Name:Title:   EXECUTED
by SPIRENT
COMMUNICATIONS OF ROCKVILLE, INC.  By:Name:Title:   EXECUTED
by HELLERMANNTYTON
CORPORATION  By:Name:Title:   EXECUTED
by HELLERMANNTYTON
CANADA INCORPORATED  By:Name:Title:


EXECUTED
by SPIRENT
COMMUNICATIONS OF OTTAWA LIMITED  By:Name:Title:   EXECUTED
by PG INTERNATIONAL PLC  By:Name:Title:   EXECUTED
by HELLERMANNTYTON DATA
LIMITED  By:Name:Title:   EXECUTED
by SPIRENT
COMMUNICATIONS (SCOTLAND) LIMITED  By:Name:Title:   EXECUTED
by SPIRENT
COMMUNICATIONS (SW) LIMITED  By:Name:Title:   EXECUTED
by SPIRENT
COMMUNICATIONS LIMITED  By:Name:Title:


EXECUTED
by SPIRENT HOLDINGS
CORPORATION  By:Name:Title:   EXECUTED
by SPIRENT FINANCING
CORP.  By:Name:Title:   EXECUTED
by NETCOM SYSTEMS
HOLDINGS CORPORATION  By:Name:Title:   EXECUTED
by SPIRENT OVERSEAS
LIMITED  By:Name:Title:


ANNEX
1  CURRENT
NOTEHOLDERS  Series A Notes  Name of Noteholder
  
  Principal
  Amount of Notes HeldThe
  Travelers Insurance Company
  
  $
  5,467,312.91
  Series B
Notes  Name of Noteholder
  
  Principal
  Amount(s) of Notes HeldConnecticut
  General Life Insurance Company
  
  $
  11,944,461.95Life
  Insurance Company of North America
  
  $
  2,571,036.00Massachusetts
  Mutual Life Insurance Company
  
  $
  11,426,826.67Primerica
  Life Insurance Company
  
  $
  1,714,024.00The
  Travelers Insurance Company
  
  $
  8,570,120.01
  Series C
Notes  Name of Noteholder
  
  Principal
  Amount(s) of Notes HeldMetropolitan
  Life Insurance Company
  
  $
  33,804,997.13Metropolitan
  Tower Life Insurance Company
  
  $
  4,583,728.42Metropolitan
  Property and Casualty Insurance Company
  
  $
  4,583,728.42Teachers
  Insurance and Annuity Association of America
  
  $
  22,918,642.11
  Series D
Notes  Name of Noteholder
  
  Principal
  Amount(s) of Notes HeldSwiss Re
  Life & Health America Inc
  
  $
  1,164,566.35The Lincoln
  National Life Insurance Company
  
  $
  14,611,813.99Lincoln Life &
  Annuity Company of New York
  
  $
  291,141.59First
  Penn-Pacific Life Insurance Company
  
  $
  1,164,566.35
  1


ANNEX
2  INFORMATION
AS TO COMPANY AND SUBSIDIARIES  Part 4.2
  
  Financial Indebtedness[See attached spreadsheet]  2


SPIRENT
PLC AND ITS SUBSIDIARIES  FINANCIAL
INDEBTEDNESS AS OF AS AT 31 DECEMBER 2004  TOTAL O/DRAFT
  FACILITIES
  AVAILABLE
  (000)
  
  TOTAL LOAN
  FACILITIES
  AVAILABLE
  (000)
  
  OVERDRAFT
  BALANCE AS AT
  31-Dec-04
  (000)
  
  LOAN
  BALANCE AS AT
  31-Dec-04
  (000)
  
  TOTAL
  OUTSTANDING
  31-Dec-04
  GBP (000)SECURED
  
  855
  
  3,306
  
  724
  
  3,044
  
  3,768UNSECURED
  
  6,010
  
  95,815
  
  80
  
  65,198
  
  65,278FINANCE LEASES
  
  
  
  
  
  
  
  9,559
  
  9,559TOTAL
  
  6,866
  
  99,121
  
  804
  
  77,801
  
  78,605UNSECURED SPIRENT PLC INDEBTEDNESS
  
  6,000
  
  95,009
  
  
  
  65,009
  
  65,009TOTAL SUBSIDIARY FINANCIAL INDEBTEDNESS
  
  £
  866
  
  £
  4,112
  
  £
  804
  
  £
  12,792
  
  £
  13,596


ANNEX
3  [See attached letter agreement dated February 18, 2004]  3


SPIRENT plc  18 February 2004  To each of the Current Noteholders Named in Annex 1 hereto:  With
reference to (i) the Amendment and Consent Agreement dated as of December 31,
2003 (the "Amendment Agreement"; all capitalized terms used herein
without definition to have the meanings assigned thereto in the Amendment
Agreement), among you and Spirent plc (the "Company") and (ii) the
New Bank Facility, the Company hereby agrees that it shall, no earlier than
December 31, 2004 but prior to January 30, 2005, exercise the Term-Out Option
contained in the New Bank Facility unless prior to such exercise date the New
Bank Facility has been extended or refinanced so as to comply with the provisions
of Section 9.8 of the Note Purchase Agreement. 
Immediately after exercising such Term-Out Option, the Company shall
give the Current Noteholders and their special counsel Bingham McCutchen LLP
written notice of such exercise.  Any
breach of this letter agreement shall constitute an Event of Default under the
Note Purchase Agreement.  Very truly yoursSPIRENT PLCBy:
  /s/ Eric HutchinsonName: Eric HutchinsonTitle: Director


EXHIBIT A  AMENDMENTS  §1Amendmentsto Section 7.1(B) of the
Existing Note Purchase Agreement.Section 7.1(B) of
the Existing Note Purchase Agreement is hereby amended by deleting the word and
at the end of Section 7.1(B)(j), deleting the period and inserting the
word ;and at the end of Section 7.1(B) (k) and by adding a new
7.1(B)(1) in its appropriate place in such Section:  (l)Conference Call  by
way of a conference call conducted on a semi-annual basis within seven days of
receipt by the Noteholders of the Companys annual statements or semi-annual
statements, as the case may be, by the group finance director of the Company
with the Noteholders and their special counsel, an update on the Groups
financial performance.  §2Amendmentto Section 10.3 of the
Existing Note Purchase Agreement.Section 10.3 of the Existing Note Purchase Agreement is
hereby amended and restated in its entirety to read as follows:  10.3 Liens, etc.  The Company will not, and will not permit any
of its Subsidiaries to, directly or indirectly create, incur, assume or permit
to exist (upon the happening of a contingency or otherwise) any Lien on or with
respect to any property or asset (including, without limitation, any document
or instrument in respect of goods or accounts receivable) of the Company or any
such Subsidiary (and in no event shall any amounts outstanding under the Bank
Facility, any Committed Medium-Term Financing or any Committed External
Financing be secured by any Liens) whether now owned or hereafter acquired, or
any income or profits therefrom or assign or otherwise convey any right to
receive income or profits unless it makes, or causes to be made, effective
provision whereby the Notes will be equally and ratably secured with any and
all other obligations thereby secured, (x) such security to be granted (i) no
later than the date upon which the Lien is granted, and (ii) pursuant to
an agreement reasonably satisfactory to the Required Holders and (y) if such
obligations are the Bank Facility, any Committed Medium-Term Financing or any
Committed External Financing, the holders of such obligations shall have
entered into an intercreditor agreement with the Noteholders satisfactory in
form, scope and substance to each Noteholder in its sole discretion and, in any
case, the Notes shall have the benefit to the fullest extent that, and with
such priority as, the holders of the Notes may be entitled under applicable
law, of an equitable Lien on such property, except:  (a)Liens existing as of December 31, 2002 and
described in Schedule 5.13;  (b)Liens for taxes or assessments or other
applicable governmental charges or levies not yet delinquent or which are being
contested as permitted by Section 9.4;  (c)Liens created or arising by operation of law in
the ordinary course of business, including, without limitation, landlords
liens and statutory liens of carriers, warehousemen, mechanics, materialmen,
vendors and other Liens securing amounts which are not yet due or which are
being contested on a timely basis in good faith by  A-1


appropriate means (so long as the enforcement of any such
Lien shall be stayed during such contest) and for which appropriate reserves or
similar provision have been made under Applicable GAAP;  (d)Liens incurred or deposits made in the ordinary
course of business in connection with workers compensation, unemployment
insurance and other types of social security or to secure the performance of
tenders, statutory obligations, surety or appeal bonds, bids, leases,
government contracts, performances in return of money bonds and similar
obligations;  (e)easements, rights-of-way, zoning and similar
restrictions and other similar Liens not materially impairing the value of the
property to which such restrictions or other similar Liens attach or
interfering with the ordinary conduct of the business of the Company and its
Subsidiaries;  (f)any attachment or judgment Lien unless the
judgment it secures shall not, within 60 days after the entry thereof, have
been discharged or execution thereof stayed pending appeal, or shall not have
been discharged within 60 days after the expiration of any such stay;  (g)Liens in favor of banks or other depository
institutions arising in the ordinary course of business from statutory rights
of set-off;  (h)Liens encumbering goods and documents of title
with respect to such goods and arising in the ordinary course of business in
connection with the issue of documentary letters of credit, in each case not
incurred or made in connection with the borrowing of money or the obtaining of
advances or similar credit, and Liens arising out of title retention provisions
in a suppliers standard condition of supply of goods acquired in the ordinary
course of business (so long as the obligations that are material and are owing
to such supplier are not overdue);  (i)Liens in respect of property of any Subsidiary
in favor of the Company or another Wholly-Owned Subsidiary;  (j)in the case of any Person that after the date
hereof is acquired by or consolidated with or merged with or into the Company
or any Subsidiary, Liens existing at the time such Person is so acquired,
consolidated or merged (and not incurred in anticipation thereof), or in the
case of any property or assets acquired by the Company or any Subsidiary after
the date hereof, Liens existing on such property or assets at the time of
acquisition thereof (and not incurred in anticipation thereof), whether or not
the Financial Indebtedness secured thereby is assumed by the Company or such
Subsidiary, provided that:  (i)no such Lien shall extend to or cover any other property of
the Company or such Subsidiary, as the case may be; and  (ii)the Company shall cause such Lien to be discharged within
180 days after the effective date of such acquisition, consolidation or merger;  (k)Liens in respect of property or assets
(including real property) acquired or developed by the Company or any
Subsidiary after the date hereof, which Liens are  A-2


created at the
time of acquisition or on or before completion of development of such property
or assets, to secure Financial Indebtedness assumed or incurred to finance all
or any part of the purchase price or cost of developing such property or
assets, provided that:  (i)no such Lien shall extend to or cover any other property or
assets of the Company or such Subsidiary, as the case may be; and  (ii)the principal amount of the Financial Indebtedness secured
by all such Liens in respect of any such property or assets shall not exceed
the lesser of the Fair Market Value (determined at the time of acquisition or
development) or the cost of such property or assets;  (l)extensions, renewals or replacements of any
Lien permitted by clause (a) or (k) of this Section 10.3 in
connection with extensions, renewals or refundings of the Financial
Indebtedness secured thereby (including the undrawn portion of facilities set
forth in Schedule 5.13) so long as the principal amount of such Financial
Indebtedness or facility is not increased and such Lien as so extended, renewed
or replaced does not extend to or cover any property other than the property
covered thereby immediately prior to such extension, renewal or replacement;
and  (m)other Liens to the extent not otherwise
permitted by clauses (a) through (l) of this Section 10.3, inclusive,
provided that the sum of (i) the
aggregate amount of the Financial Indebtedness and other obligations of the
Group secured by Liens other than Liens listed on Schedule 5.13 except to
the extent the principal amount secured by such Lien exceeds the amount stated
in such Schedule, plus (without
duplication) (ii) Total Subsidiary Debt at such time, does not exceed
£30,000,000 (or its equivalent in other currencies) at such time.  Notwithstanding the foregoing provisions of
this Section 10.3, the Company shall not, and shall procure that no member
of the Group shall, create or allow to exist any Lien on any of its assets in
favor of a Person securing any amounts outstanding under the Bank Facility, the
New Bank Facility, the 2005 Bank Facility, any Committed Medium-Term Financing,
any Committed External Financing or any bank or other creditor financing
facility replacing such facility or any part of such facility, regardless of
the principal amount or the committed amount secured or the scheduled final
maturity date thereof.  If any member of
the Group intends to create, creates or permits to subsist any Lien on any of
its assets in violation of the preceding sentence, the Company shall ensure, by
no later than the date on which such Lien is granted, that (x) the relevant
member of the Group executes such security and intercreditor documentation as
the Required Holders may require to ensure that all the obligations under the
Financing Documents shall be secured by the same assets and shall rank pari passu with the other obligations
secured on those assets, or (y) at the request of the Company, such other
security and intercreditor documentation in respect of any other assets of the
Group as the Required Holders shall agree, provided
that in the case of both (x) and (y) such violation shall nevertheless
constitute an Event of Default.  A-3


§3Amendmentto Section 10.4(b) of the
Existing Note Purchase Agreement.Section 10.4(b) of
the Existing Note Purchase Agreement is hereby amended and restated in its
entirety to read as follows:  (b)Prior
to the Normalization Date, the Company will not, and will not permit any Subsidiary
to, make any Transfer without the prior written consent of the Required Holders
except for Permitted Disposals
and Asset Dispositions permitted under Section 10.2; provided that,
notwithstanding the terms hereof, no Transfer will be permitted under this Section 10.4(b) if
it is otherwise prohibited by the terms of the 2005 Bank Facility or any
replacement bank or other credit or financing facility in respect thereof.  §4Amendmentto Section 10.4(c) of the
Existing Note Purchase Agreement.Section 10.4(c) of
the Existing Note Purchase Agreement is hereby amended and restated in its
entirety to read as follows:  (c)On
and after the Normalization Date, except as permitted under Section 10.2
of this Agreement, the Company will not, and will not permit any Subsidiary to,
make an Asset Disposition unless:  (i)in the good faith opinion of the Company, the Asset
Disposition is in the best interest of the Company or such Subsidiary;  (ii)immediately after giving effect to the Asset Disposition, no
Default or Event of Default would exist; and  (iii)immediately after giving effect to the Asset Disposition,
the Net Proceeds Amount arising from all Asset Dispositions of all property
that was the subject of any Asset Disposition occurring on and after the Effective
Date would not exceed £25,000,000.  If the Net Proceeds Amount received in
respect of any Transfer is applied to a Debt Prepayment Application or a
Property Reinvestment Application within 365 days after such Transfer, then
such Net Proceeds Amount shall be excluded for the purpose of determining
compliance with clause (c) of this Section 10.4 as of any date.  Notwithstanding the foregoing, no Asset
Disposition will be permitted under this Section 10.4(c) if it is
otherwise prohibited by the terms of the 2005 Bank Facility or any replacement
bank or other credit or financing facility in respect thereof.  §5Amendmentto Section 10.7(d) of the
Existing Note Purchase Agreement.Section 10.7(d) of
the Existing Note Purchase Agreement is hereby amended and restated in its
entirety to read as follows:  (d)Required
Additional Subsidiary Guarantees. 
The Company will not permit any Subsidiary (other than a Subsidiary that
is a Guarantor) to enter into, incur, grant or be or become liable under or
otherwise permit to exist any Guaranty in respect of any Financial Indebtedness
(other than the Financial Indebtedness evidenced by the Notes), unless a
Subsidiary Guarantee has been granted by such Subsidiary in favor of the
holders of the Notes in respect of the obligations of the Company under and
pursuant to this Agreement and the Notes and such Subsidiary has otherwise
complied with the provisions of clause (b) of this Section 10.7.  A-4


§6Amendmentto Section 10.11(b) of
the Existing Note Purchase Agreement.Section 10.11(b) of
the Existing Note Purchase Agreement is hereby amended and restated in its
entirety to read as follows:  (b)Acquisitions
on and after the Normalization Date. 
On and after the Normalization Date, the Company will not, and will not
permit any of its Subsidiaries to, make an Acquisition or commit to make an
Acquisition whether for cash, shares or other consideration unless the group
finance director of the Company certifies to the holders of the Notes that such
Acquisition would not on a pro forma basis have resulted in the Company
breaching any of the financial covenants set out in this Agreement (and as in
effect on and after the Normalization Date) on either of (i) the two
Testing Dates immediately prior to and (ii) the two Testing Dates (based
on the Companys projections) immediately after the proposed date of the
Acquisition.  For the purpose of
calculating pro forma financial information for purposes of this Section 10.11(b) for
a period ending on a Testing Date, it shall be assumed that the Acquisition
shall have occurred on the first day of the Accounting Period (which for the
avoidance of doubt shall be a twelve month period) ending on the applicable
Testing Date.  Notwithstanding the foregoing, the Company
will not, and will not permit any of its Subsidiaries to, make any Acquisition:  (a)(except
pursuant to clause (a)(i) or clause (a)(iii) above)
during the continuance of an Event of Default under this Agreement whether
before or after the Normalization Date; or  (b)if any such Acquisition would be otherwise prohibited by the
terms of the 2005 Bank Facility or any replacement bank facility.  §7Amendments to Schedule B
of the Existing Note Purchase Agreement.Schedule B of the
Existing Note Purchase Agreement is hereby amended by replacing each of the
following defined terms in its appropriate place in alphabetical order in such
Schedule:  Committed Medium-Term Financing  means a
loan, credit or financing facility or facilities (including an extension to the
2005 Bank Facility) providing for revolving or term loans pursuant to a written
commitment by one or more banks or other financial institutions or any other
external debt financing entered into by the Company, in each case with a
maturity or maturities of no earlier than February 1, 2006, providing for
aggregate total commitments of not less than £30,000,000.  Designated Debt Subsidiaries  means On-Site
Limited (provided that at least
90% of all of its Voting Shares, other equity interests and voting interests
are at all times owned directly or indirectly by the Company (except directors
qualifying shares and shares or other equity interests owned by directors or
employers to the extent such ownership is required to comply with applicable
local law or regulation)), HellermannTyton (Pty) Limited (provided that at least 90% of all of its
Voting Shares, other equity interests and voting interests are at all times
owned directly or indirectly by the Company (except directors qualifying
shares and shares or other equity interests owned by directors or employers to
the extent such ownership is required to comply with applicable local law or
regulation)), HellermannTyton Pte Limited (provided
that at least 75% of all of its Voting Shares, other equity interests and
voting interests are at all times owned directly or indirectly by the Company
(except  A-5


directors qualifying shares and shares or other equity interests owned
by directors or employers to the extent such ownership is required to comply
with applicable local law or regulation)) or HellermannTyton (Wuxi) Electrical
Accessories Co. Ltd (provided
that at least 75% of all of its Voting Shares, other equity interests and
voting interests are at all times owned directly or indirectly by the Company
(except directors qualifying shares and shares or other equity interests owned
by directors or employers to the extent such ownership is required to comply
with applicable local law or regulation)).  Network Products Division  means the Companys
division comprised of the following entities: HellermannTyton (HT), divisions of Spirent plc
(divisions: HT Broadband, HT Plymouth, HT Ireland, HT BHD, HT Manchester and
the assets and business of Staeng Limited), Staeng Limited, HT Data Limited,
Spirent Australia pty Limited, HellermannTyton GmbH, HellermannTyton S.A.,
HellermannTyton pty Limited, HellermannTyton AB, HellermannTyton Limitada,
HellermannTyton Srl, HellermannTyton Corporation, Spirent BVs interest in
HellermannTyton Pte Limited (75%), Spirent plcs interest in Tyton Corporation
of Japan (49%) and all Subsidiaries of such companies.  Permitted Bank  means:  (a)any commercial bank or trust company having, in
respect of its long-term unsecured debt obligations, a rating of A or higher
by Standard & Poors or IBCA or A-2 or higher by Moodys or a
comparable rating from a nationally recognized (in England) credit rating
agency; or  (b)the Bank Agent, so long as its ultimate parent
shall have in respect of its long-term unsecured debt obligations, a rating of A-
or higher by Standard & Poors or IBCA or A-3 or higher by
Moodys or a comparable rating from a nationally recognized (in England) credit
rating agency.  Systems - Drive Division  means the business
and assets of PG DrivesTechnology Limited owned by Spirent plc, PG
International plc, PG Drives Technology Limited and PG Drives Technology Inc.  §8Amendment to Schedule B
of the Existing Note Purchase Agreement.  Schedule B of the Existing Note Purchase
Agreement is hereby amended by adding the following defined terms in its
appropriate place in alphabetical order in such Schedule:  Bank
Agent  means Lloyds TSB Bank plc or any successor
or replacement entity acting as agent under the 2005 Bank Facility or any
replacement bank facility.  New
Bank Facility  means the £30,000,000 credit
facility entered into by the Company dated February 4, 2004.  2005
Bank Facility  means the £30,000,000 credit
facility entered into by the Company dated February 2, 2005, and as in
effect on February 2, 2005.  A-6


§9Amendmentto Exhibit B of the Existing
Note Purchase Agreement.  Exhibit B of the Existing Note Purchase
Agreement is hereby amended and restated in its entirety to read as follows:  EXHIBIT B  FORM OF
NORMALIZATION CERTIFICATE  To:Each of the Noteholders
listed on Schedule A hereto  From:Spirent plc  Date:  SPIRENT plc
(formerly BOWTHORPE plc) Amended and
Restated Note Purchase Agreement  This is a Normalization Certificate.  The Company hereby represents and warrants as of the date hereof that:  1.On
three consecutive Normalization Testing Dates (as such term is defined in the
Amended and Restated Note Purchase Agreement, as amended from time to time (the
Agreement), dated as of March 11, 2003, between Spirent plc (the Company)
and the Noteholders listed on Schedule A hereto; capitalized terms used
herein without definition have the respective meanings specified in the
Agreement), the Companys ratio of Consolidated Net Debt, as of each such
Normalization Testing Date, to Consolidated EBITDA, for the Accounting Period
ending on such Normalization Testing Date, was less than 1.5 to 1.0.  The relevant Normalization Testing Dates and
ratios are set out below:  Normalization Testing Date
  
  Ratio of Consolidated Net Debtto Consolidated EBITDA  2.On
the same three consecutive Normalization Testing Dates as mentioned in paragraph
1 above, the Companys ratio of Consolidated EBITA to Consolidated Net Interest
Expense, in each case determined for the Accounting Period ending on such
Normalization Testing Date, was in excess of 4.5 to 1. The relevant
Normalization Testing Dates and ratios are set out below:  Normalization Testing Date
  
  Ratio of Consolidated EBITAto Consolidated Net Interest Expense  3.The
Company has obtained Committed Medium-Term Financing(s) with                       
[fill in names(s) of bank(s)/financial institution(s)], with a
maturity/maturities of no earlier than February 1, 2006, providing for
aggregate total commitments of not less than £30,000,000.  The principal terms and conditions of such
Committed Medium-Term Financing(s) are set out on Schedule B hereto.  4.No
Default or Event of Default has occurred which is continuing.  Schedule C contains supporting calculations in reasonable detail
with respect to the representations and warranties contained in paragraphs 1
and 2 hereof.  A-7


SPIRENT PLCBy:Name:Title:[group finance director]  A-8


Schedule A  Metropolitan Life Insurance Company  Metropolitan Tower Life Insurance Company  Metropolitan Property and Casualty Insurance Company  Teachers Insurance and Annuity Association of America  The Lincoln National Life Insurance Company  Lincoln Life & Annuity Company of New York  First Penn-Pacific Life Insurance Company  The Travelers Insurance Company  Primerica Life Insurance Company  Connecticut General Life Insurance Company  Life Insurance Company of North America  Massachusetts Mutual Life Insurance Company  Swiss Re Life & Health America Inc   [To be updated as required at
the time of delivery to
accurately reflect the Noteholders at such time.]  A-9


Schedule B  [tobe provided by the Company]  A-10


Schedule C  [tobe provided by the Company]  A-11