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Browse Prior Art Database

Direct Inward Outward Dialing Trunk Circuit

IP.com Disclosure Number: IPCOM000091846D
Original Publication Date: 1968-Jun-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 43K

Publishing Venue

IBM

Related People

Balourdet, LG: AUTHOR [+2]

Abstract

A special line of a public telephone network is connected to PBX extensions for automatic operation on incoming and outgoing calls. Direct dialing is a rather complex function requiring line supervision and special signaling. Such occurs as if the PBX trunk circuit is integrated into the central exchange CX organization. Line seizure by the PBX or the CX, local or toll calls, permanent line supervision, etc., require a great number of messages to be exchanged between the PBX and its CX in both directions.

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Direct Inward Outward Dialing Trunk Circuit

A special line of a public telephone network is connected to PBX extensions for automatic operation on incoming and outgoing calls. Direct dialing is a rather complex function requiring line supervision and special signaling. Such occurs as if the PBX trunk circuit is integrated into the central exchange CX organization. Line seizure by the PBX or the CX, local or toll calls, permanent line supervision, etc., require a great number of messages to be exchanged between the PBX and its CX in both directions.

This direct inward-outward dialing trunk circuit provides for different conditions. In an idle condition, there is detection of idle current flowing through the line and informing the CX of any failure, either automatically or following an instruction from the PBX Control Unit CU. In a direct outward dialing DOD status, there are various CU instructions and CX signals. There is sending to CX the PBX Seize signal. There is receiving the CX acknowledgement and closing the DOD loop for DC. But, if after PBX Seize signal sending, the CX sends back a CX Seize signal and not an acknowledgement, one PBX call is cancelled. Priority is given to CX calls. There is making out dialing pulse numbering. There is a recalling if wanted, of a CX operator. Charge metering pulses are detected. There is releasing the trunk and then putting it back in idle position after CX recognition. In direct inward dialing DID status, there are the following CX signals and CU instructions. A CX Seize signal is detected. Inward dialing pulses in local or toll calls are received.

Signals required by the CX procedure are sent to CX. These are End of Numbering which is an acknowledgement of inward dialing reception, Off-Hook of the wanted PBX extension, Recall of the CX Operator, On-Hook of the extension, and detecting the CX Release signal and then returning the trunk in idle position.

The DID-DOD trunk comprises line transformer LT and associated circuitry, internal DC detector Y scan-point, network loss adjustment LA and voice limiter VL, charge metering circuit CM, and electro mechanical and logical circuits, which realize the required DIU-DOD functions. The latter circuitry has various portions. There are the Alarm and Out-Dialing relay AOD and its control circuits. In idle condition, the relay, normally operated, opens the b wire of the telephone line to inform CX of a trunk failure, external or internal.

In DOD call, it dials...