Abstract: Method and apparatus for synchronizing local clocks at each of two data stations. The first data station is connected through an analog network to an interworking unit. The second data station is connected through an integrated services network having a central clock, to the interworking unit. The interworking unit includes a comparator for comparing the clock phase from the first station transmit clock to the central clock. The result of the comparison is transmitted to the second data station for use in synchronizing the second data station to the first data station.

Abstract: Disclosed is a full duplex communication system connecting by a two wire link a main station and a local station. Both the main station and the local station has a clock pulse generator. The local clock pulse generator is switchable between a pulse rate which corresponds to that of the main clock and another pulse rate which defers about a fixed value. A comparator compares the phase of the incoming signal with the local clock signal and switches the local clock generator when its output is out of phase with the received signals.

Abstract: A data transmission path comprises a first and a second station, a first data transmission channel operative for synchronously transmitting data from the first to the second station in synchronism with a predetermined clocking schedule and at a respective first maximum data transmission rate, and a second data transmission channel for asynchronously transmitting data from the second to the first station at a respective second maximum data transmission rate, the first maximum data transmission rate being equal to a multiple p of the second maximum data transmission rate. A test waveform is applied to the first station for transmission to the second station along the first data transmission channel, the test waveform presenting a data transmission rate at least approximately equal to said first maximum data transmission rate.