Apparatus for detecting in-band single frequency signaling tones

Details Apparatus for detecting in-band single frequency signaling tones Apparatus for detecting in-band single frequency signaling tones

1984-03-26

1986-05-20

Orsino, Jr., Joseph A.

Multiplex communications

Wide area network

Packet switching

3701101, 370 50, H04J 114, H04J 312

Patent

active

045905959

ABSTRACT:
A time-division multiplexed (TDM) signal carrying speech information and in-band single frequency signaling tones is simultaneously applied to a digital band-pass filter and a digital band-elimination filter. The signaling tone components of the TDM signal are passed through the band-pass filter, while they are eliminated by the band-elimination filter. First and second digital rectifiers convert the outputs of band-pass and band-elimination filters into first and second single-polarity TDM signals, and integrated by first and second digital integrators to generate first and second integrator outputs having mutually distinguishable digital values. A digital comparator compares the integrator outputs with each other and generates a TDM comparator output when the first integrator output is greater than the the other by a predetermined amount. A verifying circuit is provided for sequentially detecting the duration of a series of digital bits in each time slot of the TDM comparator output specified by the location of the channel in which the signaling tone is generated and sequentially verifying that the detected duration exceeds a predetermined duration.

REFERENCES:
patent: 3710028 (1973-01-01), Pitroda
Kikuchi et al., "A Study on Digital Pushbutton Signaling Receiver", Review of the Electrical Communication Laboratories, vol. 27, No. 7-8, Jul.-Aug. 1979, pp. 630-641.

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