Telegraphy – Systems – Printing
Patent
1975-07-31
1977-08-02
Sloyan, Thomas J.
Telegraphy
Systems
Printing
178 88, 307233R, 325320, 328140, 340347DD, H03K 906, H03K 1324
Patent
active
040399591
ABSTRACT:
A decoder for converting a frequency coded digital input signal into a binary output signal. The decoder includes circuitry which detects when the input signal consists of the proper tones. When these tones are present, the decoder circuitry converts the tone signals into constant amplitude squarewave signals. The squarewave signals are then attenuated and integrated, and these two signals are offset and applied to a comparator. The resulting signal from the comparator is in the form of a pulse signal having rectangular pulses of constant amplitude and width, with the repetition rate of the pulses being equal to the corresponding tone frequency. The rectangular pulse signal is filtered and converted into a binary signal having binary levels which correspond to the average value of the filtered pulse signal with respect to an adjustable reference value. The noise response of the decoder is dependent upon the energy in a noise signal rather than just the amplitude, thus the decoder is highly immune to false decoding due to short noise pulses.
REFERENCES:
patent: 3223929 (1965-12-01), Hofstad et al.
patent: 3307112 (1967-02-01), Clark
patent: 3315094 (1967-04-01), Mills
patent: 3353102 (1967-11-01), Meyers et al.
patent: 3412205 (1968-11-01), Saeger
patent: 3581220 (1971-05-01), Bell et al.
patent: 3746993 (1973-07-01), Ahmed et al.
patent: 3801918 (1974-04-01), Milne et al.
Analog Devices, Inc., ANALOG-DIGITAL CONVERSION HANDBOOK, 6/1972, pp. III-32, 33.
Sloyan Thomas J.
Smith R. W.
Westinghouse Electric Corporation
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