Modem with low part count and improved demodulator

Details Modem with low part count and improved demodulator Modem with low part count and improved demodulator

1982-12-13

1984-02-14

Rubinson, G. Z.

179 2DP, H04M 1100

Patent

active

044318677

ABSTRACT:
An FSK modem for coupling a standard data port (50) to a telephone line (45) in which the signal path between the phone line and the data port passes through a processor (55). The same frequency detection apparatus (83, 192, 180) is used to both demodulate FSK encoded signals and detect the presence of a telephone ringing signal on the line. A pair of impedances (161, 162) provide alternate paths either through an input filtering network (167) or bypassing the network (135, 69) in a manner which allows the ring signals to pass directly to the input (69) of the frequency detector while assuring that only filtered FSK signals reach the input. Also shown is the use of the same frequency synthesizing apparatus (86, 253, 259) for generating FSK output signals and high group DTMF signals with appropriate switchable attenuation (88) provided in this signal path.

REFERENCES:
patent: 3684832 (1972-08-01), Marguth, Jr.
patent: 3832637 (1974-08-01), Alexander et al.
patent: 3852531 (1974-12-01), Fretwell et al.
patent: 4330687 (1982-05-01), Foulkes et al.

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