Browse Prior Art Database

Modem Eliminator Cable for Communications Port Link Tests

IP.com Disclosure Number: IPCOM000099569D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Owens, RW: AUTHOR

Abstract

The figures illustrate a device used to connect two com- puter serial data communication ports for purposes of testing the ports or monitoring activity at the ports. The device provides a visual indication of electrical signal status at each port without requiring any external power supply.

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Modem Eliminator Cable for

Communications

Port

Link Tests

       The figures illustrate a device used to connect two com-
puter serial data communication ports for purposes of testing the
ports or monitoring activity at the ports.  The device provides a
visual indication of electrical signal status at each port without
requiring any external power supply.

      Fig. 1 shows that the device comprises an electrical cable 1
which joins two connectors 2, each of which contains visible LED
(Light Emitting Diode) indicators 3.  Connectors 2 may mate either
with cables that are attached to the communications ports to be
tested or directly to the ports themselves.

      Cable 1, which joins the two connectors 2, is wired to meet the
needs of the specific application but, in general, resembles the
schematic shown in Fig. 2.  This wiring pattern is similar to that
provided by so-called "null modem" cables and is not unique to this
device.  Additional wiring is included to connect LED indicators 3 to
the individual signal wires 1a, 1b, etc., that are to be monitored.
LED indicators 3 may be mounted within the connector housing if space
permits; otherwise, they may be secured to cable 1.

      Each LED indicator 3 is attached at its anode to its associated
signal wire 1a, etc.  The cathode of LED 3 is attached to one end of
a resistor 4.  The other end of resistor 4 is attached to a signal
ground wire 5 in connector 2.

      LED indicators 3 are typically...