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                                                                     EXHIBIT 4.2


                            CERTIFICATE OF AMENDMENT

                   OF RESTATED CERTIFICATE OF INCORPORATION OF

                                PLANTRONICS, INC.

               Plantronics, Inc. (the "COMPANY"), a corporation organized and
existing under the General Corporation Law of the State of Delaware ("DGCL"),
certifies as follows:

               FIRST: At a meeting of the Board of Directors of the Company,
resolutions were duly adopted setting forth a proposed amendment of the Restated
Certificate of Incorporation of the Company, declaring said amendment to be
advisable, and directing that such amendment be considered at the next annual
meeting of the Company's stockholders. The resolution setting forth the proposed
amendment is as follows:

               NOW, THEREFORE, BE IT RESOLVED: That Article Four, Section 4.1,
Part 1, subsection (v) of the Company's Restated Certificate of Incorporation be
amended to read in its entirety as follows: "(v) 100,000,000 shares of
undesignated Common Stock, par value $0.01 per share (the "Common Stock")";

               SECOND: The Annual Meeting of Stockholders of the Company (the
"ANNUAL MEETING") was called and held upon notice in accordance with Section 222
of the DGCL. At the Annual Meeting, the necessary number of shares as required
by statute were voted in favor of such amendment.

               THIRD: Said amendment has been duly adopted in accordance with
Section 242 of the DGCL.


               IN WITNESS WHEREOF, the Company has caused this Certificate of
Amendment to be signed by Kevin A. Goodwin, a duly authorized officer of the
Company, as of May 23, 2000.


                                  PLANTRONICS, INC.


                                  By:
                                            /s/ KEVIN A. GOODWIN
                                     ------------------------------------
                                      Kevin A. Goodwin
                                      Vice President--Legal, Senior General
                                      Counsel & Secretary

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