UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 6-K
REPORT OF FOREIGN PRIVATE ISSUER
PURSUANT TO RULE 13a-16 OR 15d-16
UNDER THE SECURITIES EXCHANGE ACT OF 1934
For the month of May , 2007
SPIRENT COMMUNICATIONS plc
_____________________________________________________________________
(Translation of registrant's name into English)
Spirent House, Crawley Business Quarter, Fleming Way, Crawley, West Sussex
RH10 9QL, UK.
_____________________________________________________________________
(Address of principal executive offices)
Indicate by check mark whether the registrant files or will file annual reports
under cover Form 20-F or Form 40-F.
Form 20-F X Form 40-F.....
Indicate by check mark whether the registrant by furnishing the information
contained in this Form is also thereby furnishing the information to the
Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.
Yes ..... No X
If "Yes" is marked, indicate below the file number assigned to the registrant
in connection with Rule 12g3-2(b): 82- ________
Form TR-1 with annex. FSA Version 2.1 updated April 2007
TR-1: Notification of Major Interests in Shares
1. Identity of the issuer or the underlying issuer of
existing shares to which voting rights are attached: Spirent Communications plc
2. Reason for notification (yes/no)
An acquisition or disposal of voting rights X
An acquisition or disposal of financial instruments which may result in the
acquisition of shares already issued to which voting rights are attached
An event changing the breakdown of voting rights
Other (please specify):______________
3. Full name of person(s) subject to notification BlackRock, Inc
obligation:
4. Full name of shareholder(s) (if different from
3):
5. Date of transaction (and date on which the
threshold is crossed or reached if different): 22nd May 2007
6. Date on which issuer notified: 25th May 2007
7. Threshold(s) that is/are crossed or reached: Gone above 5%
8: Notified Details
A: Voting rights attached to shares
Class/type of Situation previous to Resulting situation after the triggering transaction
shares the triggering
transaction
If possible use Number of Number of Number of Number of voting rights Percentage of voting
ISIN code shares voting shares rights
rights
Direct Indirect Direct Indirect
GB0004726096 N/A N/A N/A N/A 44,428,430 N/A 5.04%
B: Financial Instruments
Resulting situation after the triggering transaction
Type of financial Expiration date Exercise/ conversion No. of voting rights Percentage of voting
instrument period/date that may be acquired rights
(if the instrument
exercised/converted)
Total (A+B)
Number of voting rights Percentage of voting rights
44,428,430 5.04%
9. Chain of controlled undertakings through which the voting rights and /or the
financial instruments are effectively held, if applicable:
BlackRock Investment Management (UK) Limited - 44,428,430 (5.04%)
Proxy Voting:
10. Name of proxy holder:
11. Number of voting rights proxy holder will cease
to hold:
12. Date on which proxy holder will cease to hold
voting rights:
13. Additional information:
14 Contact name: Thomas Hone
15. Contact telephone name: 020 7743 2098
C: Additional information
Contact at Issuer: Michael Anscombe, Deputy Company Secretary, Spirent
Communications plc
Telephone: 01293 767672
Signatures
Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned, thereunto duly authorized.
______MICHAEL ANSCOMBE______
(Registrant)
Date: 29 May, 2007 By ____/s/ Michael Anscombe____
(Signature)*