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Wrap Test and Protective Devices for Line Interface Circuit

IP.com Disclosure Number: IPCOM000051984D
Original Publication Date: 1981-Apr-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Bersac, JM: AUTHOR [+2]

Abstract

This testing circuit is to be used for locating a faulty device when a failure occurs in the transmission of interface signals between a data terminal equipment (DTE) and a data communication equipment (DCE).

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Wrap Test and Protective Devices for Line Interface Circuit

This testing circuit is to be used for locating a faulty device when a failure occurs in the transmission of interface signals between a data terminal equipment (DTE) and a data communication equipment (DCE).

During an exchange of interface signals between the driver (DRV) in the DTE and the receiver (RCV) in the DCE, if the signals "Request to Send", "Ready for Sending", "Clear to Send" are faulty or not present, it is necessary to locate the failure.

The various causes of faulty operation are:
.line cut off or erroneously connected;
.line shorted at ground, at a positive voltage, or at a negative voltage;
.a faulty component in the transmitting or receiving part.

To determine what kind of failure has occurred, an additional local receiver circuit 1 (Fig. 1) is connected to node A. When a failure is to be located, the system is switched in wrap-test mode where the output signals ECHO DATA are analyzed.

Depending upon their values, as a function of the input signal DATA IN, as can be seen in the timing diagram (Fig. 2), the type of failure is identified.

The diode connected between driver output and node A protects the driver circuit against faulty positive voltages coming from the line.

The clamp circuit connected to node A avoids excessive power dissipation at the driver circuit level by an inhibit action when faulty negative voltages come from the line.

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