Signal transmission system over bidirectional transmission line

Claim 2

A signal transmission and receiving system comprising: a transmission line bidirectional along its entire length; impedance means terminating each end of said transmission line; first and second line driver circuits, each having an output circuit connected at a respective point on said transmission line, a first state presenting effectively an open circuit to said transmission line and a second state for applying a current signal to the transmission line causing a corresponding voltage signal on the transmission line; and a receiver circuit having an input circuit connected to said transmission line and responding to the presence or absence of a voltage signal on said transmission line exceeding a predetermined threshold value caused by any one of said line driver circuits for forming, respectively, first and second output signals, each line driver circuit being characterized in said second state for changing the current on the transmission line so as to change in a predetermined direction the voltage level, if any, on the transmission line caused by current from another line driver circuit.

Claim 3

A signal transmission and receiving system according to claim 1 wherein said line driver circuits each comprise a sufficiently high output impedance that the level of current applied thereby is essentially independent of voltage level on said transmission line caused by current from the other driver circuit.

Claim 4

A signal transmission and receiving system according to claim 1 wherein said line driver circuits each comprise a terminal connected to a source of potential and switching means having an output impedance which is much greater than the impedance of said transmission line, said switching means being operative for connecting said source through the output impedance thereof to the transmission lIne for applying a current signal thereto.

Claim 5

A signal transmission and receiving system according to claim 3 wherein said line driver circuit comprises a transistor having collector and emitter electrodes, the collector and emitter electrodes being coupled to said transmission line and said source, respectively, said transistor being switchable into and out of conduction for applying current pulses to said line, an additional control transistor having base, emitter and collector electrodes, the collector electrode being coupled to a source of potential and the emitter electrode being coupled to the emitter electrode of the first transistor, and circuit means for applying control signals between the base electrodes of said first and control transistors causing a relative potential difference which biases the first transistor into a conductive condition and thereby cause the first transistor to apply a current signal to said transmission line.

Claim 6

A signal transmission and receiving system according to claim 4 wherein the base electrode of the first transistor is coupled to a source of potential and the base electrode of the control transistor is coupled to a control means for biasing the base of the control transistor to different levels relative to the potential of the base of the first transistor and thereby cause the first transistor to be switched into and out of conduction.

Claim 7

A signal transmission and receiving system according to claim 4 including a separate biasing resistor coupled between the base electrode of each of said transistors and said source of potential coupled to the collectors of said transistors.

Claim 8

A signal transmission and receiving system according to claim 6 including a diode coupled in series with each of said resistors to cause the source of potential coupled to the collectors to be effectively disconnected therefrom in the event of a power failure in the source.

Claim 9

A signal transmission and receiving system according to claim 1 wherein the driver switching circuit and receiver circuit are unclamped at the transmission line to allow the voltage signal on said line to increase with each additional current applied on the transmission line.

Claim 10

A signal transmission and receiving system comprising: a transmission line bidirectional along its entire length; impedance means terminating each end of said transmission line; first and second line driver circuits, each having an output circuit, first and second states for, respectively, applying and not applying a current signal at said output circuit, the output circuit of the line driver circuits being connected at spaced apart points from each other to said transmission line so that the current from either line driver circuit divides into a portion going through the impedance means at one end of the transmission line and a portion going through the impedance means at the other end, thereby forming a corresponding voltage on the transmission line, each line driver circuit being characterized in said second state for introducing current on the transmission line in addition to the current, if any, already present from the other line driver circuit; and a receiver circuit having an input circuit connected to said transmission line and responding to the presence or absence of a voltage signal on said transmission line exceeding a predetermined threshold value caused by one of said line driver circuits for forming, respectively, first and second output signals.

Claim 11

A signal transmission and receiving system comprising: a transmission line bidirectional along its entire length; impedance means terminating each end of said transmission line; first and second line driver circuits, each having an output circuit, first and second states for, respectively, applying and not applying a current signal at said output circuit, the output circuit of the line driver circuits being connected at spaced apart points from each other to said transmission line so that the current from either line driver circuit divides into a portion going through the impedance means at one end of the transmission line and a portion going through the impedance means at the other end, thereby forming a corresponding voltage on the transmission line, each line driver circuit being characterized in said second state for introducing current on the transmission line in addition to the current, if any, already present from the other line driver circuit; and a receiver circuit having an input circuit connected to said transmission line and responding to the presence or absence of a voltage signal on said transmission line exceeding a predetermined threshold value caused by one of said line driver circuits for forming, respectively, first and second output signals.

Claim 12

A signal transmission and receiving system comprising: a transmission line bidirectional along its entire length; impedance means terminating each end of said transmission line; a plurality of line driver circuits, each having an output circuit, first and second states for, respectively, applying and not applying a current signal at said output circuit and an input circuit for controlling the state thereof; means for connecting said output circuit of each line driver circuit at a spacEd apart point from the other line driver circuits to the transmission line enabling current from any line driver circuit to divide into a portion going through the impedance means at one end of the transmission line and a portion going through the impedance means at the other end, thereby forming a corresponding voltage on the transmission line, each line driver circuit being characterized in said second state for introducing current on the transmission line in addition to current, if any, already present from the other line driver circuits; and a plurality of receiver circuits having an input circuit, the input circuits of said receiver circuits being connected at spaced apart positions to said transmission line with at least one receiver circuit connected on each side of at least one driver circuit, each receiver circuit responding to the presence and absence of a voltage signal on the transmission line exceeding a predetermined threshold value caused by at least one of said line driver circuits for forming, respectively, first and second output signals.

Claim 13

A signal transmission and receiving system comprising: a transmission line bidirectional along its entire length; impedance means terminating each end of said transmission line; a plurality of line driver circuits, each having an output circuit, first and second states for, respectively, applying and not applying a current signal at said output circuit and an input circuit for controlling the state thereof; means for connecting said output circuit of each line driver circuit at a spacEd apart point from the other line driver circuits to the transmission line enabling current from any line driver circuit to divide into a portion going through the impedance means at one end of the transmission line and a portion going through the impedance means at the other end, thereby forming a corresponding voltage on the transmission line, each line driver circuit being characterized in said second state for introducing current on the transmission line in addition to current, if any, already present from the other line driver circuits; and a plurality of receiver circuits having an input circuit, the input circuits of said receiver circuits being connected at spaced apart positions to said transmission line with at least one receiver circuit connected on each side of at least one driver circuit, each receiver circuit responding to the presence and absence of a voltage signal on the transmission line exceeding a predetermined threshold value caused by at least one of said line driver circuits for forming, respectively, first and second output signals.

Claim 14

A communications system comprising in combination: a. a two-conductor transmission line having first and second ends, b. first fixed impedance means coupled between the two conductors at the first end of said transmission line, c. second fixed impedance means coupled between the two conductors at the second end of said transmission line, d. a first source of current pulses directly coupled between the two conductors at a first position on said transmission line, said first source of current pulses having an output impedance appreciably greater than the characteristic impedance of said transmission line, said first source of current pulses supplying first current pulses to said transmission line which divide into two portions, one portion propagating in a first direction toward the first end of said transmission line and the other portion propagating in a second direction toward the second end of said transmission line, the propogation of said two portions establishing a first potential difference between the two conductors which potential difference propagates along said transmission line in unison with the two portions of the first current pulses, the magnitude of said first potential difference being proportional to the magnitude of the first current pulses, e. a second source of current pulses directly coupled between the two conductors at a second position on said transmission line remote from said first position, said second source of current pulses having an output impedance appreciably greater than the characteristic impedance of said transmission line, said second source of current pulses supplying second current pulses to said transmission line which divide into two portions, one portion propagating in a first direction toward the first end of said transmission line and the other portion propagating in a second direction toward the second end of said transmission line, the propagation of said two portions establishing a second potential difference between the two conductors at any position on said transmission line where no potential difference exists and further establishes a third potential difference between the two conductors at any position on said transmission where the second potential difference is coincident with the first potential difference established by said first current pulses, the second potential difference propagating along said transmission line in unison with the two portions of the second current pulses, the magnitude of said second potential difference being proportional to the magnitude of the second current pulses and the magnitude of said third potential difference being equal to the sum of the first and second potential differences, and f. potential difference responsive receiver means coupled between the two conductors at a third position on said transmission line, said receiver means being threshold responsive to the potential differencE existing between the two conductors at said third position on said transmission line for detecting the presence of any potential difference exceeding the threshold level of said receiver means.

Claim 15

A communications system comprising in combination: a. a two-conductor transmission line having first and second ends, b. first fixed impedance means coupled between the two conductors at the first end of said transmission line, c. second fixed impedance means coupled between the two conductors at the second end of said transmission line, d. a first source of current pulses directly coupled between the two conductors at a first position on said transmission line, said first source of current pulses having an output impedance appreciably greater than the characteristic impedance of said transmission line, said first source of current pulses supplying first current pulses to said transmission line which divide into two portions, one portion propagating in a first direction toward the first end of said transmission line and the other portion propagating in a second direction toward the second end of said transmission line, the propogation of said two portions establishing a first potential difference between the two conductors which potential difference propagates along said transmission line in unison with the two portions of the first current pulses, the magnitude of said first potential difference being proportional to the magnitude of the first current pulses, e. a second source of current pulses directly coupled between the two conductors at a second position on said transmission line remote from said first position, said second source of current pulses having an output impedance appreciably greater than the characteristic impedance of said transmission line, said second source of current pulses supplying second current pulses to said transmission line which divide into two portions, one portion propagating in a first direction toward the first end of said transmission line and the other portion propagating in a second direction toward the second end of said transmission line, the propagation of said two portions establishing a second potential difference between the two conductors at any position on said transmission line where no potential difference exists and further establishes a third potential difference between the two conductors at any position on said transmission where the second potential difference is coincident with the first potential difference established by said first current pulses, the second potential difference propagating along said transmission line in unison with the two portions of the second current pulses, the magnitude of said second potential difference being proportional to the magnitude of the second current pulses and the magnitude of said third potential difference being equal to the sum of the first and second potential differences, and f. potential difference responsive receiver means coupled between the two conductors at a third position on said transmission line, said receiver means being threshold responsive to the potential differencE existing between the two conductors at said third position on said transmission line for detecting the presence of any potential difference exceeding the threshold level of said receiver means.