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Dial Digit Capture Algorithm for a Telephone Billing System

IP.com Disclosure Number: IPCOM000040061D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

McDonald, EJ: AUTHOR

Abstract

This invention is part of an electronic exchange telephone billing system. The purpose of the billing system is to monitor all outgoing subscriber telephone calls to 1) identify any one of 40,000 subscribers making a call, 2) record the digits dialed by the caller, 3) determine call initiation time, duration of call, and call disconnect time, and 4) properly itemize and bill the effective calls in realtime. The system is a distributed, modular, electronic telephone exchange which includes multiple main control units (MCUs) operating in load sharing mode. Each MCU can handle up to 36 new calls simultaneously. The processing of a new call includes 1) the detection of caller off-hook, 2) register assignment, 3) collection at the register of digits dialed by the calling subscriber, and 4) dial location of the register.

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Dial Digit Capture Algorithm for a Telephone Billing System

This invention is part of an electronic exchange telephone billing system. The purpose of the billing system is to monitor all outgoing subscriber telephone calls to 1) identify any one of 40,000 subscribers making a call, 2) record the digits dialed by the caller,
3) determine call initiation time, duration of call, and call disconnect time, and 4) properly itemize and bill the effective calls in realtime. The system is a distributed, modular, electronic telephone exchange which includes multiple main control units (MCUs) operating in load sharing mode. Each MCU can handle up to 36 new calls simultaneously. The processing of a new call includes 1) the detection of caller off-hook, 2) register assignment, 3) collection at the register of digits dialed by the calling subscriber, and 4) dial location of the register. The data collection portion of the telephone billing system includes a hardware monitor card (MCUM) which plugs into the MCU rack and monitors the I/O signals of the MCU as it processes telephone calls originating in the exchange. The hardware implementation of this invention resides on the MCUM card. This invention provides a method for deriving dial digits from the loop disconnect dial pulses detected in the system for up to 36 calls in progress at the same time. In the system, the MCU contains a stored program processor which counts the dial pulses which occur when a subscriber dials a digit. As each dial pulse is detected at one of the 36 "registers" assigned to the new call, the MCU maintains an accumulative count in a working store (R3) dedicated to each "register." The pulse counting operation requires that the MCU fetch the working store (R3), increment it by one, and then restore it.

The final value of R3, which occurs before an inter-digit pause occurs, represents the actual digit dialed by a subscriber. For example, if a subscriber dials a six, the states of R3 would be the following: Re:b b b b b b b 1 2 3 4 5 6 b b b b (inter-digit pause) b b b... where b = a blank character. This invention monitors the pulse counting operation in the MCU by capturing the initial, all intermediate, and the final values of R3, as R3 is manipulated by the MCU during a call. Since the MCU can theoretically handle dialing in all 36 of its registers concurrently, a small hardware DD table is used to keep track of the "growing state" of each dial digit as the MCU counts dial pulses. Each entry of the table is addressed by an index (RN) which specifies one of the 36 MCU registers being processed. The MCU samples each of its registers (i.e., RN) every 25 ms for outgoing dial digits. An RN changes every 8-1/3 ms, which is also how often the MCU register program visits a...