Multiplex communications – Wide area network – Packet switching
Patent
1983-10-06
1985-09-10
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
370 67, H04J 312, H04Q 1104
Patent
active
045410887
ABSTRACT:
In a digital PCM-TDM telephone exchange, supervisory tones needed are centrally generated by a digital synthesizer. This includes a PROM (1) in which PCM codes for the tones needed are stored in successive memory locations. The tones used are the DR tone, which is a mixture of 350 Hz and 440 Hz, and the BN tone, which is 400 Hz. These are read out under clock pulse control (5-6-7) such that the DR tone bytes are read out at time slot 0 and the BN tone bytes are read out at time slot 1. They are then sent over a common intelligence bus (4) to all line and trunk interfaces.
At each such interface the tone bytes are converted to analogue form so as to be continuously available. The tone (or tones) to be used is (or are) selected in response to instructions from the central control each of which specifies a program in the interface's processor. Such a program controls both the selection of the tone (or tones) needed, and the cadence (continuous, or interrupted in a defined manner).
REFERENCES:
patent: 3899642 (1975-08-01), Jones et al.
patent: 4205203 (1980-05-01), Mehta et al.
patent: 4227248 (1980-10-01), Munter
patent: 4399535 (1983-08-01), Southard
patent: 4480330 (1984-10-01), Magnusson et al.
Clarke Dennis P.
Kuntz Curtis
Olms Douglas W.
Standard Telephones and Cables, PLC
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