GB2130457A

GB2130457A - Method and apparatus for signal transmission

Info

Publication number: GB2130457A
Application number: GB08330354A
Authority: GB
Inventors: Sten Ake Olaus Rydborn
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-11-16
Filing date: 1983-11-14
Publication date: 1984-05-31
Also published as: JPS59156043A; GB8330354D0; IT8323719A0; SE8206506D0; SE451930B; IT1208176B; DE3341365A1; FR2536227A1; SE8206506L

Abstract

The invention relates to a method and an apparatus for the simultaneous and mutually independent transmission ot two unmodulated signals (A, B) on a single conductor (1), in which an operational amplifier (4) is feedback-coupled so that the voltage on a signal transmission conductor (1) connected to the feedback coupling circuit reflects a signal voltage (B) impressed on the operational amplifier (4) and maintains this signal voltage (B) constant and independent of possible current variations, whereby a current signal (A) is transmitted from the opposite side of the signal transmission conductor (1), so that the voltage signal (B) may be sensed on the opposite side of the signal transmission conductor (1), and the current signal (A) may be sensed on that side where the voltage signal (B) was impressed. <IMAGE>

Description

SPECIFICATION Method and apparatus for signal transmission Technical field The present invention relates to a method for the simultaneous and mutually independent transfer of two unmodulated signals on one conductor, and an apparatus for carrying out the method.

The state of the art In the simultaneous transfer of two unmodulated signals, prior art methods and apparatuses call for the provision of one conductor for each signal. This entails, in many installations, large and extensive cable clusters which not only require a great deal of space, but are also extremely costly.

Object of the invention The task forming the basis of the present invention is to realise a method and an apparatus for making possible the above-mentioned signal transmission on a single conductor.

Solution This task is solved according to the present invention in that a current signal is fed into the first end of the conductor and a voltage signal is impressed on its other end which, by the intermediary of a sensing resistor, is coupled to a circuit with return coupling from the other end of the conductor in order to maintain the voltage at the other end of the conductor equal to the voltage signal, and that the current signal is drawn across the sensing resistor or between the sensing resistor and the above-mentioned circuit, and the voltage signal is drawn on the first end of the conductor.An apparatus for carrying out this method is characterised in that an operational amplifier with one signal input and a return coupling input has its output coupled to the second end of a signal transmission conductor, by the intermediary of a sensing resistor, and is operative to maintain the voltage in the conductor in dependence of the voltage on the signal input and at constant level, by means of a return coupling from the signal transmission conductor to the return coupling input of the operational amplifier, and that the first end of the signal transmission conductor is coupled to a circuit for input of a current signal which may be sensed on the output from the operational amplifier or across the sensing resistor, while the voltage on the conductor may be sensed at the first end of the conductor.

Advantages Thus, as a result of the method and apparatus according to the present invention, it is possible to transmit, on one and the same conductor, a voltage signal and a current signal, these signals being unmodulated and being either DC signals or AC signals.

Brief description of the accompanying drawings Embodiments of the present invention will be described in greater detail below with reference to the accompanying Drawings.

Figure 1 is a principle diagram of an apparatus according to the present invention.

Figure2 is a connection diagram of two alternatiye apparatuses according to the present invention.

Description ofpreferred embodiments A single signal conductor 1 extends between a point 2 and a point 3, and the point 3 may be considered as being located to the left of the broken line 3, while the point 2 may be considered as being located to the right of the broken line 2. On this single signal transmission conductor 1, it is desirable simultaneously and mutually independently to transmit two signals A and B, the one signal A being transmitted from the point 3 to the point 2, and the signal B being transmitted from the point 2 to the point 3. The signal B is a voltage signal and the signal A is a current signal. The point 2 comprises an operational amplifier 4 which corresponds to the signal B on its positive input and whose output is, by the intermediary of a resistor 5, connected to the signal transmission conductor 1.That end of the resistor 5 coupled to the conductor 1 is, further, return coupled to the negative input of the operational amplifier 4 by the intermediary of a resistor 6.

The opposite end of the signal conductor 1 is coupled to the base of a transistor T1 and to the collector of a transistor T2. The collector of the transistor T1 is coupled to a supply voltage + and the emitter of the transistor T1 is coupled to earth by the intermediary of a resistor 7. The emitter of the transistor T1 is also the output for the signal B. Thus, the signal B on the positive input of the operational amplifier 4 may be sensed on the emitter of the transistor T1. In the circuit illustrated in Figure 1,the base of the transistor T1 is coupled to the collector of the transistor T1, while the base of the transistor T2 is coupled to the connection between two resistors 8 and 9. The emitter of the transistor T2 is coupled to an input for the signal A by the intermediary of a resistor 10.At the point 2, there is provided a further operational amplifier 11 whose negative input is coupled, by the intermediary of a diode 12, to the output of the operational amplifier 4, and to the supply voltage + by the intermediary of a resistor 13.

The connection between the diode 12 and the output of the operational amplifier 4 is coupled to the base of a transistor T3 by the intermediary of a resistor 14.

The collector of the transistor T3 is coupled to earth by the intermediary of a resistor 15, while the emitter is coupled to the signal conductor 1. The signal conductor 1 is also coupled to the positive input of the operational amplifier 11 by the intermediary of a resistor 16. The resistor 9 and the point 3 are coupled to the supply voltage + while the resistor 8 is coupled to earth.

As is illustrated in Figure 1, the voltage change realised by the signal B will occur on the signal transmittance conductor 1 and will be return coupled to the negative input of the operational amplifier 4 by the intermediary of the resistor 6. Thus, the operational amplifier 4 will, independently of the current on the signal transmission conductor 1, maintain the voltage change realised by the signal B on the conductor 1, it being possible to draw this voltage change via the emitter on the transistor T1, as illustrated at B.The current change realised by means of the signal A on the conductor 1 will not entail any change of the voltage change realised by the signal B, because of the return coupling of the operational amplifier 4, but the current signal A will give rise to a voltage across the resistor 5 which may be sensed by means of the transistor T3 and the operational amplifier 11, whereby the output of the operational amplifier 11 will emit the signal A. The uppermost circuit shown in Figure 2 illustrates a slightly simplified version and, from the slave side, an AC signal is transmitted which is fed in at the arrow A to the master side and may be sensed by the capacitor on the output of the operational amplifier.

A DC signal which is fed in on the positive input of the operational amplifier may be sensed on the slave side at B.

The lowermost circuit illustrated in Figure 2 is operative, from the slave side, to transmit a DC signal to the master side and a DC signal from the master side to the slave side. By means of the broken lines c and d, it is further illustrated that the two slave sides and the two master sides may be optionally combined with one another.

Claims

1. A method for the simultaneous and mutually independent transmission of two unmodulated signals on a single conductor, wherein a current signal is fed into a first end of the conductor; and that a voltage signal is impressed on the second end of the conductor, said second end being, by the intermediary of a sensing resistor, coupled to a circuit with return coupling from the second end of the conductor to maintain the voltage on the second end of the conductor equal to the voltage signal; and that the current signal is drawn over the sensing resistor or between the sensing resistor and said circuit, and the voltage signal is drawn on the first end of the conductor.

2. A method for the simultaneous and mutually independent transmission of two unmodulated signals on a single conductor, wherein one of the signals is a current signal applied to a first end of the conductor and the other signal is a voltage signal applied to the other end of the conductor, the second end of the conductor being coupled via a sense resistance to a circuit which also has a return or feedback coupling from the second end of the conductor whereby the voltage on the second end of the conductor is dependent upon the voltage signal but is substantially independent of changes in current on the conductor introduced by the current signal, and the voltage signal is sensed at the first end of the conductor and the current signal is sensed at the second end of the conductor.

3. A method as claimed in claim 1 or 2, wherein the current signal is sensed at the second end of the conductor by sensing changes in the voltage across the sense resistance produced by the current signal.

4. A method as claimed in claim 1,2 or 3, wherein the circuit comprises an operational amplifier the output of which is coupled to the second end of the conductor via the sense resistance, a first input of which receives the voltage signal and a second input of which receives the return or feed- back coupling from the second end of the conductor.

5. A method for the simultaneous and mutually independent transmission of two unmodulated signals on a single conductor substantially as hereinbefore described with reference to Figure 1 or Figure 2 of the accompanying drawing.

6. An apparatus for carrying out a method according to any one of claims 1 to 5, wherein said circuit comprises an operational amplifier with a signal input and a return coupling input and which has its output coupled to the second end of the signal transmission conductor by the intermediary of a sensing resistor and is operative to maintain the voltage on the conductor dependent upon the voltage on its signal input but unchanged by changes in current on the conductor, by means of a return coupling from the signal transmission con doctor to its return coupling input and that the first end of the signal transmission conductor is coupled to means for the input of the current signal which may be sensed on the output from the operational amplifier or across the sensing resistor while the voltage on the conductor may be sensed on the first end of the conductor.

7. Apparatus for the simultaneous and mutually independent transmission of two unmodulated signals on a single conductor substantially as shown in and as hereinbefore described with reference to, Figure 1 or Figure 2 of the accompanying drawing.