PROSPECTUS SUPPLEMENT
(TO PROSPECTUS DATED MARCH 26, 1999)


                               CONOLOG CORPORATION

                        3,057,143 Shares of Common Stock


                  This document  supplements the Prospectus dated March 26, 1999
relating to:

         o        1,057,143 shares of Common Stock issuable pursuant to the
                  Consulting Agreement; and

         o        2,000,000 shares of Common Stock issuable upon conversion of
                  the Convertible Debentures which are issuable upon the
                  exercise of the option granted pursuant to the Option
                  Agreement.

                  This Prospectus Supplement is incorporated by reference into
the Prospectus, and all terms used herein shall have the meaning assigned to
them in the Prospectus. The Common Stock is traded under the symbol "CNLG" on
the Nasdaq SmallCap Market. On June 18, 1999, the closing price of the Common
Stock was $1.375.

                  In accordance with the section of the Prospectus titled
"Selling Stockholders and Plan of Distribution", the following information is
provided:

                           On May 5, 1999, the Option Agreement was amended and
restated to provide:

         o        for shareholder approval of the Option Agreement prior to
                  CLOG's option being exercisable its effectiveness; and

         o        that the voting power of any Conversion Shares of Clog will be
                  voted in the same proportion as the other shares.

                  Also on May 5, 1999, the  Consulting  Agreement was amended to
provide:

         o        for shareholder approval of the Consulting Agreement prior to
                  its effectiveness; and

         o        that the voting power of the Consulting Shares owned by Nybor
                  will be voted in the same proportion as the other shares.

                  On June 17, 1999, at the Conolog Corporation Annual Meeting of
Shareholders, the shareholders approved each of the Option Agreement and the
Consulting Agreement. In addition, the shareholders also approved an amendment
to the Certificate of Incorporation to change the par value of the Common Stock
from $1.00 par value per share to $.01 par value per share.

                         ------------------------------

Neither the Securities and Exchange Commission nor any state securities
commission has approved or disapproved of these securities or has determined
whether this prospectus is truthful or complete.

                         -------------------------------

                     The date of this Prospectus Supplement
                               is June 21, 1999.