Abstract: The invention provides a circuit for monitoring predetermined performance criteria of a transmission link by measuring a predetermined ratio of events in a data stream. A first counter having a predetermined maximum count is responsive to each of periodic predetermined occurrences in the data stream and a clock pulse for also increasing its count by one. A second counter having a predetermined maximum count is responsive to each error of predetermined type in the data stream and a clock pulse for increasing its count by one. The overflow output of the first counter is connected to the clear input of the second counter and the overflow output of the second counter is connected to the clear input of the first counter. A signal appearing at the overflow output of the second counter indicates that the predetermined ratio of events in the data stream has not been met. The circuit also provides turn-on, turn-off hysteresis.

Abstract: The invention provides a data unit for the rate adaptation to overspeed data in fully digital systems adapted to the transmission of block mode asynchronous data. The data unit comprises an interface circuit for receiving data from a transmission facility, a universal asynchronous receive transmit circuit (UART) for interfacing to data terminal equipment, a dynamically adjustable baud rate generator for driving the UART, and a microprocessor for controlling the transfer of data from the transmission facility to the output of the UART. Upon detection of overspeed data being received, the frequency of the baud rate generator is increased for the remainder of the byte being processed in the UART. The baud rate generator is reset to its nominal frequency at the boundary of each byte outputted from the data unit.

Abstract: An automatic correction circuit is responsive to suitable bit patterns in a bit stream being received from a transmission medium, to generate an error amplitude map of signal distortion being introduced by the transmission medium. The error amplitude map is digitally stored or recorded. After each non zero bit occurrence in the signal stream a synchronized output signal corresponding to the recorded error amplitude map is generated and added to the bit stream being received to reduce signal distortion, whereby information recovery from the received bit stream is improved.