Apparatus for transmitting and receiving pulses

In a PCM telecommunication system, in combination:

• a subscriber line provided with a first terminal;
• a modulation channel for forming samples of low-frequency signals originating at said subscriber line and for converting said samples into outgoing code pulses, said modulation channel being provided with a second terminal;
• an active filter in said modulating channel including a first operational amplifier;
• a demodulation channel for converting incoming code pulses into low-frequency signals to be transmitted to said subscriber line, said demodulation channel including detector means and being provided with a third terminal connected to an output of said detector means;
• an active filter in said demodulation channel including a second operational amplifier;
• duplexing means for coupling said channels to said subscriber line while decoupling said channels from each other, said duplexing means comprising a resistance network forming an incoming-signal path from said third terminal to said first terminal, an outgoing-signal path from said first terminal to said second terminal, and a balancing-signal path from said third terminal to said second terminal for canceling the transmission of signals from said demodulation channel to said modulation channel via said incoming-signal and outgoing-signal paths in series;
• and
• signal-amplifying means inserted between said detector means and said third terminal for preventing the transmission of signals from said first terminal to said detector means via said incoming-signal path.

In a PCM telecommunication system, in combination:

• a subscriber line provided with a first terminal;
• a modulation channel for forming samples of low-frequency signals originating at said subscriber line and for converting said samples into outgoing code pulses, said modulation channel being provided with a second terminal;
• a demodulation channel for converting incoming code pulses into low-frequency signals to be transmitted to said subscriber line, said demodulation channel including detector means and being provided with a third terminal connected to an output of said detector means;
• duplexing means for coupling said channels to said subscriber line decoupling said channels from each other, said duplexing means comprising a resistance network forming an incoming-signal path from said third terminal to said first terminal, an outgoing-signal path from said first terminal to said second terminal, and a balancing-signal path from said third terminal to said second terminal for canceling the transmission of signals from said demodulation channel to said modulation channel via said incoming-signal and outgoing-signal paths in series;
• and
• signal-amplifying means inserted between said detector means and said third terminal for preventing the transmission of signals from said first terminal to said detector means via said incoming-signal path, said signal-amplifying means including active filter means of the Sallen-Key type having an amplitude/frequency response of low-pass type compensating for the (sin .omega..tau./2)/.omega..tau./2 distortion due to the conversion of said incoming code pulses, .omega. being the angular frequency of the low-frequency signals transmitted to said subscriber line and .tau. being the duration of each of said samples.

In a PCM telecommunication system, in combination:

• a subscriber line provided with a first terminal;
• a modulation channel for forming samples of low-frequency signals originating at said subscriber line and for converting said samples into outgoing code pulses, said modulation channel including an active filter and being provided with a second terminal and with a series capacitor inserted between said active filter and said second terminal;
• a demodulation channel for converting incoming code pulses into low-frequency signals to be transmitted to said subscriber line, said demodulation channel including detector means and being provided with a third terminal connected to an output of said detctor means;
• duplexing means for coupling said channels to said subscriber line while decoupling said channels from each other, said duplexing means comprising a resistance network forming an incoming-signal path from said third terminal to said first terminal, an outgoing-signal path from said first terminal to said second terminal, and a balancing-signal path from said third terminal to said second terminal for canceling the transmission of signals from said demodulation channel to said modulation channel via said incoming-signal and outgoing-signal paths in series;
• and
• signal-amplifying means inserted between said detector means and said third terminal for preventing the transmission of signals from said first terminal to said detector means via said incoming-signal path.

In a PCM telecommunication system, in combination:

• a subscriber line provided with a first terminal;
• a modulation channel for forming samples of low-frequency signals originating at said subscriber line and for converting said samples into outgoing code pulses, said modulation channel being provided with a second terminal;
• a demodulation channel for converting incoming code pulses into low-frequency signals to be transmitted to said subscriber line, said demodulation channel including detector means and being provided with a third terminal connected to an output of said detector means;
• duplexing means for coupling said channels to said subscriber line while decoupling said channels from each other, said duplexing means comprising a resistance network forming an incoming-signal path from said third terminal to said first terminal, an operational amplifier inserted between said network and said modulation channel, said operational amplifier having an output connected to said second terminal and further having an inverting input and a noninverting input, an outgoing-signal path from said first terminal to said second terminal, said outgoing signal path including a first branch of said network extending to one of said inputs, and a balancing-signal path from said third terminal to said second terminal for canceling the transmission of signals from said demodulation channel to said modulation channel via said incoming-signal and outgoing-signal paths in series, said balancing-signal path including a second branch of said network extending to the other of said inputs;
• and
• signal-amplifying means inserted between said detector means and said third terminal for preventing the transmission of signals from said first terminal to said detector means via said incoming-signal path.

In a PCM telecommunication system, in combination:

• a resistor line provided with a first terminal;
• a modulation channel for converting low-frequency signals originating at said subscriber line into outgoing code pulses, said modulation channel being provided with a second terminal;
• a demodulation channel for converting incoming code pulses into low-frequency signals to be transmitted to said subscriber line, said demodulation channel including detector means and being provided with a third terminal connected to an output of said detector means;
• duplexing means for coupling said channels to said subscriber line while decoupling said channels from each other, said duplexing means comprising a resistance network forming an incoming-signal path from said third terminal to said first terminal, an outgoing-signal path from said first terminal to said second terminal, and a balancing-signal path from said third terminal to said second terminal for canceling the transmission of signals from said demodulation channel to said modulation channel via said incoming-signal and outgoing-signal paths in series;
• and
• active filter means including an operational amplifier inserted between said detector means and said third terminal for preventing the transmission of signals from said first terminal to said detector means via said incoming-signal path while compensating for signal distortions occurring in said demodulation channel.