Audio-communication system having a plurality of interconnected stations

Claim 2

A multiple station audio communication system, comprising a plurality of spaced stations, a single pair of transmission lines interconnecting said stations, an audio transmitting device at each station, an audio receiving device at each station, an amplifier at each station having a relatively high impedance input means and a low impedance output means, said amplifier having a local power supply, and a talk-listen switch means at each station having a first state connecting said input means of said amplifier to said audio transmitting device and the output means to said transmission line pair and having a second state connecting the input means of said audio amplifier to said transmission lines and the output of said amplifier to the said related audio receiving device.

Claim 3

A multiple station audio communication system, comprising a plurality of spaced stations, a single pair of transmission lines interconnecting said stations, an audio transmitting device at each station, an audio receiving device at each station, an amplifier at each station having a relatively high impedance input means and a low impedance output means, said amplifier having a local power supply, and a talk-listen switch means at each station having a first state connecting said input means of said amplifier to said audio transmitting device and the output means to said transmission line pair and having a second state connecting the input means of said audio amplifier to said transmission lines and the output of said amplifier to the said related audio receiving device.

Claim 4

A multiple station audio communication system, comprising a plurality of spaced stations, a single pair of transmission lines interconnecting said stations, an audio transmitting device at each station, an audio receiving device at each station, an amplifier at each station having a relatively high impedance input means and a low impedance output means, said amplifier having a local power supply, and a talk-listen switch means at each station having a first state connecting said input means of said amplifier to said audio transmitting device and the output means to said transmission line pair and having a second state connecting the input means of said audio amplifier to said transmission lines and the output of said amplifier to the said related audio receiving device.

Claim 5

The multiple station audio communication system of claim 1 wherein at least one of said stations constitutes a master station having a remote control means for superimposing a control signal on said transmission lines for simultaneous transmission of said control signal to said other stations as controlled remote stations, each of the remote stations having a line reversal circuit having a signal sensing network responsive to said control signal and an output driving means coupled to the corresponding switch means to reverse the position thereof.

Claim 6

The audio communication system of claim 1 wherein each remote station includes a latch circuit means for connecting and disconnecting of the corresponding remote station to the transmission lines, said latch circuit means having a local input means continuously biased to a disconnect position and a coded input means connected to the master station and responsive to a selected input to connect the remote station to said transmission lines.

Claim 7

The communication system of claim 2 wherein the control signal is a direct currenT signal and said master station includes discharge means connected to said transmission lines and responsive to selected actuation of said switch means at the master station to said second state for establishing a momentary direct current discharge circuit at the master station across said transmission lines for discharging capacitive energy stored in said transmission lines.

Claim 8

The communication system of claim 4 wherein discharge means includes a gated solid state switch connected across said transmission lines and a gating network operatively connected across said transmission lines with said switch means in said second state.

Claim 9

The communication system of claim 2 wherein control signal is a direct current voltage and said remote control means includes a line charge and discharge circuit, second switch means coupled to said first switch means at said master station and actuated simultaneously therewith, said line charge and discharge circuit having a pair of current limiting resistors connected to said transmission lines and to a direct current supply by said second switch means, said discharge circuit including an electronic switch connected across said lines to the input side of said resistors, a capacitor in series with a sensing resistor connected across said electronic switch means in series with said second switch means and establishing a signal at the junction of the capacitor and sensing resistor to fire said electronic switch means, a discharge resistor connected across said capacitor and resistor in series with the said second switch means to discharge any residual capacity in the capacitor upon switching of the master station to the talk position.

Claim 10

The communication system of claim 6 wherein said first state of said second switch means is a master station talk position and said second state is a master station listen position.

Claim 11

The communication system of claim 2 wherein said control signal is a direct current voltage and said line reversal circuit includes an operational amplifier having a first input, a high impedance coupling circuit means connected to said first input and to said transmission lines, said amplifier having a second input connected to a DC reference voltage at the corresponding station, the output of said operational amplifier being coupled to control an electronic driver stage in series with said switch means, and a manual control switch connected in parallel with said electronic driver stage to provide for direct energization of the switching means operator.

Claim 12

The communication system of claim 2 wherein the control signal is a direct current voltage and said remote control means includes a direct current supply, second switch means coupled to said first talk-listen switch means and actuated simultaneously therewith, a pair of current limiting resistors connected to said transmission lines and to said direct current supply by said second switch means, a discharge circuit including a gated unidirectional electronic switch connected across said lines, a gating circuit connected to actuate said electronic switch to discharge stored energy on said transmission lines, said second switch means selectively connecting said gating circuit across said transmission lines, said line reversal circuit includes an operational amplifier having a first high impedance input connected to said transmission lines and a second input connected to a direct current reference voltage at the corresponding station, the output of said operational amplifier being coupled to control an electronic driver in series with said talk-listen switch means, and a manual control switch connected in parallel with said electronic driver to provide for direct energization of the corresponding talk-listen switch means.

Claim 13

The communication system of claim 9 wherein said high impedance input includes a pair of series coupling resistors and a parallel resistor connected between said transmission lines and the inputs of operational amplifier.

Claim 14

The communication sYstem of claim 9 wherein said gated electronic switch is a controlled rectifier means connected across said direct current supply and to said transmission lines in series with said resistors, said gating circuit includes a firing capacitor in series with a sensing resistor connected across said controlled rectifier in series with said second switch means and having the junction of the capacitor and sensing resistor connected to the gate of the rectifier means.

Claim 15

The communication system of claim 11 having a discharge resistor connected across said capacitor and resistor in series with said second switch means to discharge any residual capacity in the firing capacitor upon movement of the master station switch means to a selected position.

Claim 16

A multiple station audio communication system, comprising a plurality of spaced stations, a single pair of transmission lines interconnecting said stations, audio transmitting means at each station, audio receiving means at each station, an amplifier at each station having a relatively high impedance input means and a low impedance output means, said amplifier having a local power supply, switch means at each station for selectively connecting said audio transmitting means and said audio receiving means to said amplifier and said amplifier to said transmission lines for selectively and alternatively transmitting and receiving voice signals over said transmission lines, at least one of said stations constituting a master station having a remote control means connected to said other stations as controlled remote stations and each of the remote stations having a line reversal circuit responsive to the remote control means and coupled to the corresponding switch means to reverse the position thereof.

Claim 17

A multiple station audio communication system, comprising a plurality of spaced stations, a single pair of transmission lines interconnecting said stations, audio transmitting means at each station, audio receiving means at each station, an amplifier at each station having a relatively high impedance input means and a low impedance output means, said amplifier having a local power supply, switch means at each station for selectively connecting said audio transmitting means and said audio receiving means to said amplifier and said amplifier to said transmission lines for selectively and alternatively transmitting and receiving voice signals over said transmission lines, at least one of said stations constituting a master station having a remote control means connected to said other stations as controlled remote stations and each of the remote stations having a line reversal circuit responsive to the remote control means and coupled to the corresponding switch means to reverse the position thereof.

Claim 18

The communication system of claim 13 wherein each remote station includes a latch circuit means for selectively connecting said stations to said master station, and a code signal source at the master station for actuating said latch circuit means.

Claim 19

The system of claim 13 wherein said remote control means establishes a direct current voltage signal and said line reversal circuit includes an operational amplifier having a first input, a high impedance coupling circuit means connected to said first input and to said transmission lines, said operational amplifier having a second input connected to a direct current reference voltage at the corresponding station, the output of said operational amplifier being coupled to control said switch means, and a manual control means at the remote station connected to provide for direct energization of the switch means.

Claim 20

A multiple station audio communication system, comprising a plurality of spaced stations having audio transmitting and audio receiving devices at each station, transmission lines connecting said stations, switch means at each station for selectively connecting said audio transmitting device and said audio receiving device to said transmission lines, at least one of said stations constituting a master station having a remote control means and having a direct current source for superimposing a DC control signal on said transmission lines for simultaneous transmission of said control signal to said other stations as controlled remote stations, each of the remote stations having a line reversal circuit including a DC signal sensing network and an output driving means coupled to the corresponding switch means to reverse the position thereof, said master station having a line discharge means for discharging of the DC energy stored in the transmission lines, and switch means selectively connecting the direct current source and the line discharge means to the transmission lines.

Claim 21

A multiple station audio communication system, comprising a plurality of spaced stations having audio transmitting and audio receiving devices at each station, transmission lines connecting said stations, switch means at each station for selectively connecting said audio transmitting device and said audio receiving device to said transmission lines, at least one of said stations constituting a master station having a remote control means and having a direct current source for superimposing a DC control signal on said transmission lines for simultaneous transmission of said control signal to said other stations as controlled remote stations, each of the remote stations having a line reversal circuit including a DC signal sensing network and an output driving means coupled to the corresponding switch means to reverse the position thereof, said master station having a line discharge means for discharging of the DC energy stored in the transmission lines, and switch means selectively connecting the direct current source and the line discharge means to the transmission lines.