Abstract: A dictating machine control unit includes apparatus connected to a telephone transmission line and adapted to respond to signals received over the telephone line for controlling the operating functions of a dictating machine, such signals being produced by operation of a telephone instrument, which may be either the coded tone type or the dial type. The apparatus responds to the detection of a ringing signal received over the transmission line for generating a guard tone and recording the same on a record medium to identify the beginning of a recording and to serve as a buffer, providing security for previously recorded messages. The functions of "record," "play back," "review," "stop," "correction mark," "end of letter mark," and "cell attendant" are controlled in response to touch tone signals or dial pulse signals generated by operation of the telephone instrument.