NDLI: Automatic dialing and electronic selection on railroad message and dispatcher circuits

Content Provider	IEEE Xplore Digital Library
Author	Jorgensen, Otto A.
Copyright Year	2012
Abstract	Low-level tone-signal techniques are used for automatic calling and selection on multiparty single-line facilities. The subscribers, equipped with transistorized transmitters and receivers, transmit single tone signals for seizure, dialing, and release. These signals are propagated along the wires to the terminal equipment, where they are converted to d-c pulses and stored for interpretation. This interpretation is accomplished by relay logic in order to decide whether the call is for a party on the same line, or for a party within the PBX (Private Branch Exchange) to which the line is terminally connected. In the first case, the called number is converted into an amplitude-modulated tone, where the frequency of the carrier and the modulation correspond to the first and second significant digits dialed, respectively. This tone is then retransmitted for selection of the desired party. At the called subscriber's station, the electronic selector receiver, which takes the place of the electromechanical selector, responds only to the particular carrier corresponding to its number. In this receiver, the envelope is detected and the recovered modulation tone is amplified directly to drive one out of a maximum of five tuned ringers. A total of 60 stations can be used on one pair of wires having a maximum attenuation of 30 db (decibels).
Starting Page	204
Ending Page	208
Page Count	5
File Size	1531859
File Format	PDF
ISSN	00972452
Volume Number	80
Issue Number	3
Language	English
Publisher	American Institute of Electrical Engineers
Publisher Date	1961-07-01
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Receivers Relays Oscillators Switches Frequency modulation Transmitters Telephone sets
Content Type	Text
Resource Type	Article

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3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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