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Common Scanner for Circuit Switching Unit

IP.com Disclosure Number: IPCOM000096477D
Original Publication Date: 1963-Jun-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 1 page(s) / 13K

Publishing Venue

IBM

Related People

Peavy, WR: AUTHOR

Abstract

In electronic circuit switching systems, the status of lines and trunks, with respect to request for service ad other supervisory signals, is usually detected by scanning the lines and detecting tone signal presence or absence. This line scanner scans the lines on a time divided basis. Such is at a microsecond rate compared with millisecond rates of other types of line scanning systems. This scanner uses the computational filter described in AIEE Paper No. CP 63-265, ``Sampled Data Filtering As Applied to Time Multiplex Switching'' by P. Thrasher.

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Common Scanner for Circuit Switching Unit

In electronic circuit switching systems, the status of lines and trunks, with respect to request for service ad other supervisory signals, is usually detected by scanning the lines and detecting tone signal presence or absence. This line scanner scans the lines on a time divided basis. Such is at a microsecond rate compared with millisecond rates of other types of line scanning systems. This scanner uses the computational filter described in AIEE Paper No. CP 63-265, ``Sampled Data Filtering As Applied to Time Multiplex Switching'' by P. Thrasher.

Keying tones on 125 subscriber lines are seven different frequencies, e. g., 700, 1100, 1300, 1500, 1700 and 2600 cycles per second. Presence or absence of one frequency denotes the presence or absence or a command instruction on one line. Computational filter 12 accomplishes rapid sequential sampling of each line for the frequencies. The filter 12 outputs are inputs to threshold detector 14 which detects the presence or absence of one frequency. The detector 14 outputs are supplied to filter buffer register 16 which stores the detected signals.

Scan counter 24 is stepped sequentially to control scanning of the 125 lines and selection from switching memory 20 of the corresponding previous status for the line presently scanned. Address register 26 decodes the counter 24 output to address the word from memory which contains the previous status of the line presently scanned. Scan decoder 28 decodes the counter 24 output to address one of the 125 input lines to be gated through a gate 30. When a subscriber line is sampled by one output 32 of decoder 28, a binary word containing the ...