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 June, 2006

                       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- ________




Spirent Communications plc announces that they have put in place an irrevocable,
non-discretionary programme allowing the buy back of Spirent Communications plc
shares during the close period which precedes the interim results announcement
on 10th August 2006. Any purchases pursuant to these arrangements will be
effected during the period between 3rd July 2006 and 10th August 2006 within
certain pre-set parameters and will be in accordance with the company's general
authority to repurchase shares.

Any shares repurchased will be held as Treasury shares. In announcing this
Spirent Communications plc confirms that currently it has no unpublished price
sensitive information.

                                   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.

                                               ______LUKE THOMAS______

                                                     (Registrant)

Date 30 June 2006                           By   ____/s/ Luke Thomas____

                                                    (Signature)*