Browse Prior Art Database

Communications Monitor Circuit

IP.com Disclosure Number: IPCOM000091132D
Original Publication Date: 1969-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Althauser, WE: AUTHOR [+3]

Abstract

The circuit provides for a Monitor mode for an attendant to monitor line conditions, including the presence of audio signals without loading or interfering with the line. An Interrupt mode is also provided in which two-way conversation is possible between the attendant and a dictator at a remote station.

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Communications Monitor Circuit

The circuit provides for a Monitor mode for an attendant to monitor line conditions, including the presence of audio signals without loading or interfering with the line. An Interrupt mode is also provided in which two-way conversation is possible between the attendant and a dictator at a remote station.

The monitor circuit is at A with a mode control circuit at B and additional details at C. The circuit at A and C includes corresponding terminals designated a1, a2, b, c, and d. Monitor phone 1 is connected by terminal b to the circuit. Ordinarily, when phone 1 is on-hook, no current flows through transistor 3, at C. Therefore, the emitter of transistor 3 is low and the FTX transistor 4 provides no output. When the attendant lifts the receiver of phone 1, voltage is supplied to the collector of transistor 3 from terminal b to activate it and develop a fairly large voltage across resistor
2. This turns on FTX transistor 4 to supply voltage from terminal d. Signals from communication lines 5 and 6, particularly 5, are directed to terminal a1 and transistors 7 and 8 for listening by the attendant from terminal b.

In Interrupt mode, the dictator customarily indicates a wish to converse by signalling the attendant. This provides potential to terminal 10, at B, to energize reed relays R1 and R2 through magnet drivers 11 and 12. This transfers contacts R1-1 and R2-1. Closure of the R2-1 contacts completes a circuit through terminals c and...