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Eia RS232 and RS422 Wrap Plug Test and Differentiation

IP.com Disclosure Number: IPCOM000061521D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 54K

Publishing Venue

IBM

Related People

Hunter, SW: AUTHOR [+2]

Abstract

Shorting or wrap plug connectors are often used with data communications devices to check operability of transmission and reception facilities by connecting output to input during a test. The plugs are manually installed and are normally removed when the device is ready for service. This article describes a technique of providing shorting contacts in a test plug for the RS232 standard pin connector interface that enable the machine being tested to detect the presence of a plug, the identity of the type of plug installed since both RS232C and RS422 connector plugs will fit the same connections, and also provides an LED (light-emitting diode) light signal output that can be used for showing proper operability of the circuit.

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Eia RS232 and RS422 Wrap Plug Test and Differentiation

Shorting or wrap plug connectors are often used with data communications devices to check operability of transmission and reception facilities by connecting output to input during a test. The plugs are manually installed and are normally removed when the device is ready for service. This article describes a technique of providing shorting contacts in a test plug for the RS232 standard pin connector interface that enable the machine being tested to detect the presence of a plug, the identity of the type of plug installed since both RS232C and RS422 connector plugs will fit the same connections, and also provides an LED (light-emitting diode) light signal output that can be used for showing proper operability of the circuit. The figure illustrates in tabular form some of the pins present in the normal RS232 25-pin connector interface. As shown, interconnections are provided between pins 23 and 7 which connect the data rate select to the signal ground, between pins 2 and 3 which connect transmitted data to received data, between pins 4, 5 and 8 which connect request to send to clear to send and carrier detect, between pins 6 and 20 which connect data set ready to data terminal ready, between pins 17 and 24 which connect the DCE source receive and transmit clocks, and between pins 15, 18 and 22 which connect the DCE source transmit clock to test request and the ring indicator. The connection between the test request pin 18 and ring indicator on pin 22 provides a facility usable during a special port testing mode of operation of the communications device to search for the presence of a wrap plug by scanning the various pins and checking the status of the ring indicator signal. If a connection is made, a signal from the test request line 18 will appear on the ring indicator line. Firm connection can be examined by toggling the test request line on and off and checking for the status of the ring indicator line each time. If the wrap plug is found to be present and installed, a sequence of further tests can be done on drivers and receivers. If an error is found while testing, it is necessary to know whether the error is caused by hardware or by the inadvertent removal of the wrap plug. This can be decid...