# US 4,400,589 A · Subscriber station network

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- Number: US 4,400,589 A
- Document ID: US4400589A
- Status: Granted
- Kind: A
- Application number: 06/283,116
- Filed: 1981-07-13
- Granted: 1983-08-23
- Earliest claimed: 1979-05-21
- Assignees: United Networks, Inc.; Manu-Tronics, Inc.
- Inventors: Jan Synek; Michael Tentler
- Web page: https://patentgrep.com/patent/US4400589A

## CPC

- H04M 1/76: Compensating for differences in line impedance
- H04M: TELEPHONIC COMMUNICATION (circuits for controlling other apparatus via a telephone cable and not involving telephone switching apparatus G08)

## Abstract

A solid state network for subscriber station is amenable to hybridization and mass production, minimizing costly, heavy components, facilitating transmission and reception of communication signals almost independently of variation in line impedance, and controlling a sidetone level with in-phase signals, through the use of as few as one transmitting transistor that is in series with the transmitter and also in series with the receiver, and as few as one receiving transistor.

## Claims

### Claim 1

An improved subscriber station network for a telephone system including telephone lines for connecting said subscriber station to other telephone subscriber stations,
said telephone system comprising at least two lines having a DC potential therebetween,
telephone receiver means for receiving communications from said lines,
telephone transmitter means for transmitting communication signals over said lines,
the improvement characterized in that a transmitter transistor means is provided in a series circuit with said transmitter means,
said series circuit coupled between said at least two lines,
means connecting said transmitter transistor to said receiver means to control the level of the signal passing through said receiver means,
bridge means for maintaining one of said at least two lines at a positive potential and the other of said at least two lines at a negative potential,
receiver transistor means provided in said receiver means, and
means for connecting said receiver transistor means through said receiver means to said transmitter means where said transmitter means connects said transmitter transistor means to said series circuit.

### Claim 2 (depends on 1)

The subscriber station network of claim 1 wherein said receiver transistor is connected as an emitter follower.

### Claim 3 (depends on 1)

The subscriber station of claim 1 wherein said transmitter transistor is connected as a constant current source.

### Claim 4 (depends on 1)

The subscriber station network of claim 1 wherein the emitter of said receiver transistor is coupled to said receiver means, said network including a first sidetone controlling resistor paralleling said receiver means, and a second sidetone controlling resistor in the series circuit between said transmitter means and said transmitter transistor.

### Claim 5 (depends on 4)

The subscriber station network of claim 4 wherein the base of said receiver transistor is coupled to the positive one of said at least two lines, the collector of said transmitter transistor also being coupled to the positive one of said at least two lines.

### Claim 6 (depends on 5)

The subscriber station network of claim 5 wherein a voltage divider network is provided between said two lines, the base of said transmitter transistor being connected to said voltage divider network, the emitter of transmitter transistor being connected through said second sidetone controlling resistor to said transmitter means and a third sidetone controlling resistor bridging said second sidetone controlling resistor in series with said transmitter means to connect to the negative one of said at least two lines.

### Claim 7 (depends on 1)

The subscriber station network of claim 1 including a junction between said transmitter means and said transmitter transistor means, means for connecting said receiver means to said junction, and means for connecting said receiver means to the one of said at least two lines that is at a positive potential to apply signals from the transmitter means to both ends of said receiver means in an in-phase relationship whereby the amount of cancellation of the in-phase signals determines the amplitude of the side-tone.