Abstract: For use in conjunction with a system for producing, at a transmitter location, time division multiplexed (TDM) frames having a plurality of channels of information signals and framing signals, communicating the frames from the transmitter location to a receiver location, and, at the receiver location, deframing the received frames to obtain frame timing signals and a bitstream of information signals which are coupled with a plurality of operating units. A technique for responding very quickly, upon loss of the TDM signal, to prevent misoperation of the operating units, including: at the transmitter, inserting a preselected pattern of bits in a timeslot of the information signals; at the receiver, detecting, in the deframed bit stream, the absence of the preselected pattern of bits, and producing a control signal in response; and producing override information signals that are coupled to the operating units when the control signal is present.

Abstract: The disclosed technique has application for use in conjunction with a system for producing, at a transmitter location, time division multiplexed (TDM) frames comprising a plurality of channels of information signals and framing signals, communicating the frames from the transmitter location to a receiver location, and, at the receiver location, deframing the received frames to obtain frame timing signals and a bitstream of information signals which are coupled with a plurality of operating units, for example teleprotection units.