Voltage-isolating, keying arrangement for a power-line carrier system

Claim 1

An improved power line carrier keying arrangement comprising: a. relaying means having input and output terminals, said input terminals being adapted to be connected to a power system for receiving an indication of a selected condition in said power system, and said output terminals producing keying signals in response to said selected condition; b. a keying input circuit comprising: 1. first and second input terminals; 2. means connecting said first and second input terminals to said relaying means output terminals; 3. a voltage breakdown circuit including a first resistor connected between said first input terminal and a first junction, and a first zener diode connected between said first junction and said second input terminal; 4. a capacitor connected in parallel with said first zener diode; 5. a second resistor connected in parallel with said capacitor; 6. a voltage threshold circuit including a second zener diode and a third resistor connected in a first series circuit between said first junction and said second input terminal; 7. a fourth resistor; 8. a light-emitting diode; 9. a transistor having an emitter, a collector, and a base; 10. means connecting said transistor emitter and collector, said light-emitting diode and said fourth resistor in a second series circuit between said first junction and said second input terminal; 11. a fifth resistor; 12. means serially connecting said fifth resistor between said transistor base and a common connection of said second zener diode and said third resistor in said first series circuit for causing said second series circuit to conduct current in response to said keying signals causing said first series circuit to conduct current, thereby causing said light-emitting diode to emit light energy; c. a keying output circuit comprising: 1. a first light-sensing transistor having an emitter, a collector, and a base; 2. power means connected to said light-sensing transistor emitter and collector for supplying an operating potential thereto; 3. a first resistor serially connected between said power means and said collector of said light-sensing transistor; 4. a second resistor serially connected between said emitter of said light-sensing transistor and a first output terminal of said keying output circuit; 5. a second transistor having an emitter, a collector, and a base; 6. means connecting said emitter of said second transistor to said power means, said collector of said second transistor being connected to a second output terminal of said keying output circuit; 7. means connecting said base of said second transistor to said collector of said first light-sensing transistor for supplying an output signal at said second output terminal of said keying output circuit in response to emitter collector current conduction of said light-sensing transistor; d. and means positioning said keying input circuit and said keying output circuit in spaced relation so that said lightsensing transistor base can receive light produced by said light-emittiNg diode, and produce an output signal in response to light produced by said light-emitting diode.