Browse Prior Art Database

Data Set Mode Control

IP.com Disclosure Number: IPCOM000092295D
Original Publication Date: 1968-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Johnson, RB: AUTHOR

Abstract

A data set having an external telephone handset uses the high DC on-hook impedance of the handset to determine the status of the handset and to control the mode of operation of the data set. The three modes of operation, talk, data, and auto-answer, can therefore be provided by only two buttons, talk and data, on the data set.

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Data Set Mode Control

A data set having an external telephone handset uses the high DC on-hook impedance of the handset to determine the status of the handset and to control the mode of operation of the data set. The three modes of operation, talk, data, and auto-answer, can therefore be provided by only two buttons, talk and data, on the data set.

Circuitry is provides which attempts to pass a DC current through the handset. Because the handset provides an extremely high DC impedance when on-hook and a low DC impedance when off-hook, off-hook conditions are met if current flows. The status of the handset therefore is readily available. The on- hook off-hook status of the handset is used to control the mode of operation of the data set.

There are two ways to enter the talk mode. The connection to the communications line is made through a line relay. When the set is in the data mode, the line relay is energized and the handset is thus disconnected from the line. By pressing the talk button on the data set and having the handset in the off-hook condition, the line relay is released and the set enters the talk mode. If the data set is in the auto-answer mode, pressing the talk button places the set in the talk mode.

There are also two ways to enter the data mode. In the first case, the data button is pressed with the handset in the off-hook condition. Since the handset is off-hook and the line relay not energized, a DC current flows through it. A sensitive relay, pl...