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Discrete Probe Coax Line Driver

IP.com Disclosure Number: IPCOM000090166D
Original Publication Date: 1969-Feb-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Templeman, CA: AUTHOR

Abstract

Monitoring of a computer system to evaluate its operation is achieved with only minimum loading to the system by this probe connector which distinguishes either a logical 1 or 0 signal. As shown at A, the probes indicated generally at 1 are connected between selected terminals 2 on logic backpanel 3 and a remotely located monitor 4. A common connection 5 between monitor 4 and panel 3 supplies the return path for all probe signals.

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Discrete Probe Coax Line Driver

Monitoring of a computer system to evaluate its operation is achieved with only minimum loading to the system by this probe connector which distinguishes either a logical 1 or 0 signal. As shown at A, the probes indicated generally at 1 are connected between selected terminals 2 on logic backpanel 3 and a remotely located monitor 4. A common connection 5 between monitor 4 and panel 3 supplies the return path for all probe signals.

Two types of probe circuits can be used in the system. As shown at B, the circuit includes diode D1 in series with resistor R1 to establish a level matching circuit between the probe and the back panel. In addition, diode D1 serves to block any current flow that occurs due to erratic operation at the monitor. A line driver circuit including transistor T1 and R2 completes the probe.

An alternate circuit for the probe as shown at C is for an integrated circuit chip and employs a two-stage direct-coupled amplifier consisting of transistors T2 and T3. Resistor R3 in series with the base of T2 prevents excessive loading by the input network. Capacitor C1, shown dotted, can be added across R3 to speed up transition. An input voltage of one volt or less with respect to a zero reference voltage is insufficient to turn on the transistor thus signifying a 0 at the monitor. An input of two volts or more with respect to zero reference is insufficient to turn on the transistor thus signifying a 0 at the monitor. An in...