Modem with low part count and improved demodulator
First Claim
1. In a data communications adapter for connecting a data port to a telephone line and for providing angle modulated signals to said telephone line in response to data signals provided to said data port, the improvement comprising in combination:
- a first register means for storing data signals received from said data port;
a second register means for providing a frequency signal;
signal generating means connected to said second register for providing an output signal of a frequency proportional to said frequency signal;
control means responsive to a first predetermined string of said data signals at said data port to provide a first mode of operation for said data communications adapter and alternately for providing a second mode of operation for said data communications adapter;
said control means being responsive to said data signals stored in said first register means to cause said second register means to provide one of a predetermined set of said frequency output signals corresponding to one of a predetermined group of predetermined high tones for dual tone dialing when said data communications adapter is in said first mode of operation and alterately responsive to said data signals stored in said first register means for providing one of a predetermined pair of said frequency signals corresponding to one of a predetermined pair of said angle modulated signals; and
coupling means for coupling said output signal from said signal generating means to said telephone line.
5 Assignments
0 Petitions
Accused Products
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.
-
Citations
3 Claims
-
1. In a data communications adapter for connecting a data port to a telephone line and for providing angle modulated signals to said telephone line in response to data signals provided to said data port, the improvement comprising in combination:
-
a first register means for storing data signals received from said data port; a second register means for providing a frequency signal; signal generating means connected to said second register for providing an output signal of a frequency proportional to said frequency signal; control means responsive to a first predetermined string of said data signals at said data port to provide a first mode of operation for said data communications adapter and alternately for providing a second mode of operation for said data communications adapter; said control means being responsive to said data signals stored in said first register means to cause said second register means to provide one of a predetermined set of said frequency output signals corresponding to one of a predetermined group of predetermined high tones for dual tone dialing when said data communications adapter is in said first mode of operation and alterately responsive to said data signals stored in said first register means for providing one of a predetermined pair of said frequency signals corresponding to one of a predetermined pair of said angle modulated signals; and coupling means for coupling said output signal from said signal generating means to said telephone line. - View Dependent Claims (2, 3)
-
Specification