Circuit arrangement for controlling the transmission capacity of the receiving branch of a transmission system

Claim 2

In a transmission system having separate transmitting and receiving branches connected to a two-wire transmission line via a 2-to-4 wire hybrid circuit; having an echo compensation network coupled between said transmitting and receiving branches; and having an amplifier arranged for amplifying a signal in said receiving branch; the improvement comprising circuit means for controlling the transmission capacity of said receiving branch which comprises, in combination: (a) first detector means coupled to said receiving branch for producing a first signal indicating when the signal in said receiving branch is above a prescribed level; (b) second detector means coupled to said receiving branch for producing a second signal indicating when the change in said signal in said receiving branch does not exceed a prescribed value within a prescribed time; and (c) means responsive to said first and said second signals for enabling transmission through said receiving branch only when the signal applied to said receiving branch is both above said prescribed level and did not change by said prescribed value within said prescribed time.

Claim 3

The transmission system recited in claim 1, wherein said circuit means further includes: (1I) a clock pulse-controlled register having parallel inputs and parallel outputs; and (2) an adder having parallel inputs and parallel outputs, said parallel inputs of said adder being connected to corresponding parallel outputs of said register, and said parallel outputs of said adder being connected to corresponding parallel inputs of said register; and the second detector means of the circuit means includes (1) a first exclusive-OR gate having an output, a first input connected to one parallel input of said register and a second input connected to one parallel output of said register corresponding to said one parallel input; (2) a switch responsive to the output of said first exclusive-OR gate, said switch having a first input connected to a further parallel output of said register and having a second input and an output; (3) a clock-pulse-controlled bistable element having a signal input connected to said output of said switch and a non-inverting output connected to said second input of said switch; (4I) a second exclusive-OR gate having an output, a first input connected to a further parallel input of said register corresponding to said further parallel output, and having a second input connected to said output of said bistable element; and (5) an AND-gate having an output, a first input connected to said output of said first exclusive-OR gate and a second input connected to said output of said second exclusive-OR gate.

Claim 4

The transmission system recited in claim 1 wherein the transmission enabling means comprises an inverting delay element having an input connected to said output of said AND-gate, and an output; wherein said output of said delay element is the second signal and is logically gated with the first signal, the output of the logic gate forming a control signal for controlling the transmission capacity of said receiving branch.

Claim 5

The transmission system recited in claim 3, wherein the first detector means comprises means, responsive to a particular bit pattern in the parallel output of said register, for generating said first signal.

Claim 6

A transmission system having separate transmitting and receiving branches connected to a two-wire transmission line via a 2-to-4 wire hybrid circuit; having an echo compensation network coupled between said transmitting and receiving branches; and having an amplifier arranged for amplifying a signal in said receiving branch; characterized in that the amplifier includes means for controlling its amplification in digital steps by means of a digital signal and further characterized by a circuit means for controlling the transmission capacity of said receiving branch comprising means for monitoring the digital control signal for the presence of prescribed bit pattern differences in successive amplifier adjustment time periods.

Claim 7

A transmission system having separate transmitting and receiving branches connected to a two-wire transmission line via a 2-to-4 wire hybrid circuit; having an echo compensation network coupled between said transmitting and receiving branches; and having an amplifier arranged for amplifying a signal in said receiving branch; characterized in that the amplifier includes means for controlling its amplification in digital steps by means of a digital signal and further characterized by a circuit means for controlling the transmission capacity of said receiving branch comprising means for monitoring the digital control signal for the presence of prescribed bit pattern differences in successive amplifier adjustment time periods.