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Echo Check Circuit

IP.com Disclosure Number: IPCOM000091978D
Original Publication Date: 1968-Jul-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Mackie, D: AUTHOR [+2]

Abstract

It is desirable in communication circuits to continually test the transmit and receive circuits to detect errors of omission or degeneration of a signal to an unsatisfactory level. One way of making such a test is by an echo check circuit in which data to be transmitted is sampled at an early point in a transmit circuit, the transmitted output signal is fed back into the received data input and the received data is sampled at some point in the receive circuit. A comparison of the two samples for disagreement detects errors or degradation of the circuits to an unsatisfactory point.

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Echo Check Circuit

It is desirable in communication circuits to continually test the transmit and receive circuits to detect errors of omission or degeneration of a signal to an unsatisfactory level. One way of making such a test is by an echo check circuit in which data to be transmitted is sampled at an early point in a transmit circuit, the transmitted output signal is fed back into the received data input and the received data is sampled at some point in the receive circuit. A comparison of the two samples for disagreement detects errors or degradation of the circuits to an unsatisfactory point.

Transmit operation latch 10 is set whenever the data set is in a transmit condition. Transmit data latch 11 is set by the occurrence of a mark in the data signal and is reset by a space signal. The complemental mark output of latch 11 passes through diode 12 and resistor 13 to the base of transistor 14 having base bias resistor 14 and collector load resistor 16. The collector of transistor 15 is connected through resistor 17 to the base of transistor 18 having collector resistor 19. Its emitter is connected to the junction of resistors 20 and 21 from the negative voltage source to ground. The voltage at the collector of transistor 18 is the output signal and is applied to the modulator-demodulator, modem, at output 22 for conversion to a transmission line signal.

The received data from the transmission line, as converted through a modem, is applied to input terminal 2...