Telephone tone signalling receiver with up-conversion of frequen

Details Telephone tone signalling receiver with up-conversion of frequen Telephone tone signalling receiver with up-conversion of frequen

1977-12-19

1979-05-08

Stellar, George G.

H04M 712

Patent

active

041538196

ABSTRACT:
A tone receiver, for receiving audio frequency tone signals typically used in telephone signalling, includes a reference frequency generator and a modulator for up-converting audio frequencies. Telephone network tone signalling is up-converted and coupled to a filter including a piezoelectric element. Alternating current signals passing through the filter indicate the presence of a tone signal of a predetermined frequency. Multiple frequency tone signals are detectable using a plurality of modulators and filters, each modulator being supplied with one of a plurality of reference frequencies. In one example, balanced modulation is used with reference frequencies being supplied in the form of square waves.

REFERENCES:
patent: 2339633 (1944-01-01), Gilman
patent: 2449391 (1948-09-01), Kogane
patent: 3243703 (1966-03-01), Wood
patent: 3576403 (1971-04-01), Sellari, Jr.
patent: 3810019 (1974-05-01), Miller

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