SUPERVISORY APPARATUS FOR PCM REGENERATIVE REPEATERS

Supervisory apparatus is provided in accordance with this invention for monitoring or supervising the operation of the repeater means present in a PCM transmission system wherein the transmitted information comprises a unipolar waveform. According to one embodiment of the present invention, select frequency components of differing character are assigned to each of the repeater means disposed along a common information transmission path present within the PCM transmission system. The supervisory apparatus provided in this embodiment of the present invention includes a supervisory transmission path adapted for the transmission of each of such select frequency components from said repeater means to a terminal portion of said PCM transmission system, supervisory circuit means interposed between each of said repeater means and said supervisory transmission path for applying only a specifically assigned one of such select frequency components from the repeater means connected thereto to said supervisory transmission path and means for selectively applying a unipolar supervisory signal to each of said repeater means disposed along said common information transmission path. The means for selectively applying a unipolar supervisory signal to each of said repeater means is adapted to produce a unipolar supervisory signal which is binary in nature and characterized by a waveform wherein the relative ratio of the duration of the segments thereof representing each binary state is varied to form at least two slowly varying frequency component. Such slowly varying frequency component comprises one of the select frequency components assigned to each of said repeater means and said unipolar supervisory signal may be produced in a manner so that each of such select frequency components is provided to said repeater means and readily discriminated. Accordingly, the remote detection of such select frequency components as present in said supervisory transmission path is determinative of the operating condition of the repeater means being supervised.