Pulsing circuit including a series switching circuit

Claim 2

In a telephone system including an exchange having switching means, a plurality of subscriber telephone sets, a telephone line individually connecting each telephone set to the switching means for selecting individual ones of said telephone lines, and a direct current power source, a pulsing circuit comprising: a control device including a coil responsive to be actuated by a current flow therethrough; a switching circuit responsive to control signals for switching between a high impedance state and a low impedance state; circuit means connecting said switching circuit and said coil in a direct current series circuit between said switching means and said power source so that said switching means can connect said series circuit to a telephone line, wherein the series circuit, and a connected telephone line and telephone set define a telephone loop connection, and wherein said switching circuit is normally in said low impedance state to actuate said control device when a closed circuit condition is present in a connected telephone set, and control circuit means coupled to said series circuit and said switching circuit so that said control circuit means detects when said telephone loop is switched from a closed to an open circuit condition and applies a control signal to said switching circuit that momentarily switches said switching circuit to said high impedance state.

Claim 3

A telephone system as defined in claim 1 wherein said switching circuit is switched to said high impedance state by said control circuit for a period of time on the order of the duration of the open circuit portion of a telephone dialing pulse.

Claim 4

A telephone system as defined in claim 2 wherein said control device is a relay.

Claim 5

A telephone system as defined in claim 2 wherein said control device is a saTurable reactor.

Claim 6

In a telephone system including an exchange having switching means, a plurality of subscriber telephone sets, a telephone line individually connecting each telephone set to said switching means for selecting individual ones of said telephone lines, and a direct current power source, a relay pulsing circuit comprising: a relay including a coil; a transformer including a primary winding and a secondary winding; a transistor; circuit means connecting the collector and emitter of said transistor, said primary winding and said relay coil in a direct current series circuit between said switching means and said power source for connecting across a telephone line; circuit means for applying a saturating forward bias to said transistor so that said transistor energizes said relay in response to a closed circuit condition in a connected telephone set, and a control circuit coupled to said transistor and said secondary winding for momentarily removing said forward bias when a signal is developed by said secondary winding indicating that a connected telephone set was open circuited.

Claim 7

In a telephone system including an exchange having switching means, a plurality of subscriber telephone sets, a telephone line individually connecting each telephone set to said switching means for selecting individual ones of said telephone lines, and a direct current power source, a relay pulsing circuit comprising: a relay including a coil; a transformer including a primary winding and a secondary winding; a transistor; circuit means connecting the collector and emitter of said transistor, said primary winding and said relay coil in a direct current series circuit between said switching means and said power source for connecting across a telephone line; circuit means for applying a saturating forward bias to said transistor so that said transistor energizes said relay in response to a closed circuit condition in a connected telephone set, and a control circuit coupled to said transistor and said secondary winding for momentarily removing said forward bias when a signal is developed by said secondary winding indicating that a connected telephone set was open circuited.

Claim 8

A relay pulsing circuit as defined in claim 5 wherein said control circuit includes: a control transistor; capacitive means coupled to the base and emitter of said control transistor; a rectifying circuit coupled between said capacitive means and said secondary winding, responsive to a preset polarity of signals across said secondary windings for applying a charge across said capacitor for rendering said control transistor conductive, and circuit means for connecting said emitter and collector of said control transistor to said other transistor so that said other transistor is rendered non-conductive when said control transistor is conductive.

Claim 9

A relay pulsing circuit as defined in claim 6 wherein: a second rectifying circuit is coupled between said secondary winding and said capacitive means, responsive to a signal across said secondary winding having a polarity opposite said preset polarity for charging the capacitive means in a direction opposite said other rectifying circuit; second capacitive means, and circuit means connecting said second capacitive means to said series circuit so that said second capacitive means stores a charge when said transistor connected in the direct current series circuit is conductive and functions to provide a current flow through said primary winding in a direction so that said first mentioned capacitive means renders said control transistor non-conductive when a connected telephone set switches from an open to a closed circuit condition.

Claim 10

A relay pulsing circuit comprising: a pair of conductors for connection to a switching circuit that connects and disconnects a direct current circuit across said pair of conductors; a pair of power terminals for connection to a direct current power source; a relay having a coil; a transformer having a primary winding and a secondary winding; first and second transistors; circuit means connecting said primary winding, said relay coil, and the collector and emitter of said first transistor in a direct current series circuit between said power terminals and said pair of conductors; biasing means connected to the base of said first transistor for applying a forward biasing signal thereto, said biasing signal having a sufficient magnitude so that said first transistor is saturated when said direct current circuit is connected across said pair of conductors; circuit means connecting the emitter and collector electrodes of said second transistor to the base and emitter of said first transistor so that said first transistor is rendered non-conductive when said second transistor is conductive; capacitive means; a rectifying circuit coupled between said secondary winding and said capacitive means responsive to a preset polarity of signals across said secondary winding for applying a charge tO said capacitive means, and circuit means connecting said capacitive means to the base and emitter electrodes of said second transistor so that when the current flow through said series circuit is interrupted a charge is developed by said capacitive means that momentarily renders said second transistor conductive.

Claim 11

A relay pulsing circuit comprising: a pair of conductors for connection to a switching circuit that connects and disconnects a direct current circuit across said pair of conductors; a pair of power terminals for connection to a direct current power source; a relay having a coil; a transformer having a primary winding and a secondary winding; first and second transistors; circuit means connecting said primary winding, said relay coil, and the collector and emitter of said first transistor in a direct current series circuit between said power terminals and said pair of conductors; biasing means connected to the base of said first transistor for applying a forward biasing signal thereto, said biasing signal having a sufficient magnitude so that said first transistor is saturated when said direct current circuit is connected across said pair of conductors; circuit means connecting the emitter and collector electrodes of said second transistor to the base and emitter of said first transistor so that said first transistor is rendered non-conductive when said second transistor is conductive; capacitive means; a rectifying circuit coupled between said secondary winding and said capacitive means responsive to a preset polarity of signals across said secondary winding for applying a charge tO said capacitive means, and circuit means connecting said capacitive means to the base and emitter electrodes of said second transistor so that when the current flow through said series circuit is interrupted a charge is developed by said capacitive means that momentarily renders said second transistor conductive.

Claim 12

A relay pulsing circuit as defined in claim 8 wherein said emitter and collector of said first transistor is connected between said relay coil and said power terminals.

Claim 13

A relay pulsing circuit as defined in claim 8 including: a second relay coil magnetically coupled to said other relay coil; a second primary winding magnetically coupled to said other primary winding, and circuit means for connecting said second relay coil and said second primary winding in said series circuit so that a coil and a winding are located in opposite legs of said series circuit to provide a balanced configuration, and so that said second coil and second primary winding are connected in a flux-aiding manner with said other coil and said other primary winding respectively.

Claim 14

A relay pulsing circuit as defined in claim 8 including: a second rectifier circuit coupled between said secondary winding and said capacitive means, responsive to a signal across said secondary winding having a polarity opposite to said preset polarity, for charging said capacitive means in a direction opposite to said first mentioned rectifying means to develop a charge across said capacitive means to render said secondary transistor non-conductive; second capacitive means, and circuit means coupling said second capacitive means to said series circuit so that said second capacitive means stores a charge when said first transistor is conductive, and discharges through said primary winding when said switching circuit is closed providing a current flow in a direction so that said first mentioned capacitive means receives a charge for rendering said second transistor non-conductive.

Claim 15

An electrical circuit comprising: a control device having a coil; switching means responsive to a control signal for switching between a high impedance state and a low impedance state; a pair of power terminals for connection to a direct current power source; a pair of input terminals for connection to a switching circuit for connecting and disconnecting a direct current circuit across said input terminals; circuit means connecting said coil and said switching means in a direction current series circuit between said power source and said input terminals so that said switching circuit is normally in said low impedance state to energize said coil when a direct current closed circuit connection is exhibited across said pair of input terminals, and control circuit means coupled to said series circuit and to said switching means so that said control circuit means detects when a direct current circuit is disconnected from said pair of input terminals to apply a control signal to said switching means to momentarily switch said switching circuit to the high impedance state.

Claim 16

An electrical circuit comprising: a control device having a coil; switching means responsive to a control signal for switching between a high impedance state and a low impedance state; a pair of power terminals for connection to a direct current power source; a pair of input terminals for connection to a switching circuit for connecting and disconnecting a direct current circuit across said input terminals; circuit means connecting said coil and said switching means in a direction current series circuit between said power source and said input terminals so that said switching circuit is normally in said low impedance state to energize said coil when a direct current closed circuit connection is exhibited across said pair of input terminals, and control circuit means coupled to said series circuit and to said switching means so that said control circuit means detects when a direct current circuit is disconnected from said pair of input terminals to apply a control signal to said switching means to momentarily switch said switching circuit to the high impedance state.

Claim 17

An electrical circuit as defined in claim 12 wherein said control circuit means includes: inductive means connected in said series circuit for providing a signal when the current flow through said series circuit is interrupted, and control circuit means coupled to said inductive means and said switching means for applying said control signal to said switching means having a controlled time duration in response to the signal from said inductive means.

Claim 18

An electrical circuit as defined in claim 13 wherein said control circuit means includes: a control transistor; capacitive means coupled to the base and emitter of said control transistor; a rectifying circuit coupled between said capacitive means and said inductive means for applying a charge across said capacitive means for rendering said control transistor conductive, and circuit means for connectinG said control transistor to said switching means so that said switching means is switched to said high impedance state when said control transistor is conductive.

Claim 19

An electrical circuit as defined in claim 14 wherein: said switching means is a transistor having its emitter and collector connected in said series circuit and a biasing circuit for forward biasing said transistor into saturation, and the emitter and collector of said control transistors are coupled to said biasing circuit for overcoming said forward bias to render the series transistor non-conductive when the control transistor is conductive.

Claim 20

An electrical circuit as defined in claim 12 wherein said control device is a relay.

Claim 21

An electrical circuit as defined in claim 12 wherein: said control device is a saturable reactor, and said control circuit means is coupled to a second coil on said saturable reactor.

Claim 22

A pulsing circuit comprising: a pair of conductors for connection to a switching circuit that connects and disconnects direct current circuits across said pair of conductors; a pair of power terminals for connection to a direct current power source; a saturable reactor having a pair of coils; first and second transistors; circuit means connecting one of said coils and the collector and emitter of said first transistor in a direct current series circuit between said power terminals and said pair of conductors; biasing means connected to the base of said first transistor for applying a forward biasing signal thereto, said biasing signal having a sufficient magnitude so that when a direct current circuit is connected across the pair of conductors the transistor is saturated; circuit means connecting the emitter and collector electrodes of said second transistor to the base and emitter of said first transistor so that said first transistor is rendered non-conductive when said second transistor is conductive; capacitive means; a rectifying circuit coupled between the other one of said coils and said capacitive means for applying a charge thereto, and circuit means connecting said capacitive means to the base and emitter electrodes of said second transistor so that when the current flow through said series circuit is interrupted a charge is developed by said capacitive means that momentarily renders said second transistor conductive.

Claim 23

A pulsing circuit comprising: a pair of conductors for connection to a switching circuit that connects and disconnects direct current circuits across said pair of conductors; a pair of power terminals for connection to a direct current power source; a saturable reactor having a pair of coils; first and second transistors; circuit means connecting one of said coils and the collector and emitter of said first transistor in a direct current series circuit between said power terminals and said pair of conductors; biasing means connected to the base of said first transistor for applying a forward biasing signal thereto, said biasing signal having a sufficient magnitude so that when a direct current circuit is connected across the pair of conductors the transistor is saturated; circuit means connecting the emitter and collector electrodes of said second transistor to the base and emitter of said first transistor so that said first transistor is rendered non-conductive when said second transistor is conductive; capacitive means; a rectifying circuit coupled between the other one of said coils and said capacitive means for applying a charge thereto, and circuit means connecting said capacitive means to the base and emitter electrodes of said second transistor so that when the current flow through said series circuit is interrupted a charge is developed by said capacitive means that momentarily renders said second transistor conductive.