Status indication circuit for shared telephone equipment

Claim 2

In a telephone system, a status indication circuit for indicating the busy-idle condition of shared call processing equipment to an access circuit attempting to complete a connection to the shared equipment, the access circuit having switching means responsive only to a voltage level which is greater than a predetermined voltage level to complete the connection, the status indication circuit comprising: first circuit means normally presenting a first voltage level to the access circuit when the shared equipment is idle and a second voltage level to the access circuit when the shared equipment is busy, only the first voltage level being greater than the predetermined voltage level, and second circuit means responsive to substantially simultaneous attempts by more than one access circuit to complete connections to the shared equipment to override the first circuit means and to present a third voltage level, which is substantially less than the second voltage level, to the access circuits.

Claim 3

A status indication circuit as claimed in claim 1 further comprising: third circuit means responsive to a completed connection of an access circuit to the shared equipment for maintaining the second voltage level substantially at a second value.

Claim 4

A status indication circuit as claimed in claim 2 wherein the third circuit means comprises a breakdown diode connected in parallel with the first circuit means, the first circuit means being connected to a battery which has an output potential which is substantially the first voltage level and being responsive to a completed connection by an access circuit to the shared equipment to reduce the voltage level to at least the second voltage level, the breakdown voltage of the breakdown diode thereby controlling the voltage difference between the first voltage level and the second voltage level.

Claim 5

In a telephone system, a status indication circuit for indicating the busy-idle condition of shared cAll processing equipment to an access circuit attempting to complete a connection to the shared equipment and having switching means responsive to a voltage level which is greater than a predetermined voltage level to complete the connection, the status indication circuit comprising: first circuit means normally presenting a first voltage level to the access circuit when the shared equipment is idle and a second voltage level to the access circuit when the shared equipment is busy, only the first voltage level being greater than the predetermined voltage level, and second circuit means responsive to a completed connection for controlling the difference between the first voltage level and the second voltage level.

Claim 6

In a telephone system, a status indication circuit for indicating the busy-idle condition of shared cAll processing equipment to an access circuit attempting to complete a connection to the shared equipment and having switching means responsive to a voltage level which is greater than a predetermined voltage level to complete the connection, the status indication circuit comprising: first circuit means normally presenting a first voltage level to the access circuit when the shared equipment is idle and a second voltage level to the access circuit when the shared equipment is busy, only the first voltage level being greater than the predetermined voltage level, and second circuit means responsive to a completed connection for controlling the difference between the first voltage level and the second voltage level.

Claim 7

A status indication as claimed in claim 4 wherein the second circuit means comprises a breakdown diode connected in parallel with the first circuit means, the first circuit means being connected to a battery which has an output potential which is substantially at the first voltage level and being responsive to a completed connection by an access circuit to the shared equipment to reduce the voltage level to at least the second voltage level, the breakdown vltage of the breakdown diode thereby controlling the voltage difference between the first voltage level and the second voltage level.

Claim 8

In a telephone system, a status indication circuit for indicating the busy-idle condition of shared call processing equipment to an access circuit attempting to complete a connection to the shared equipment, the access circuit having switching means responsive only to a voltage level which is greater than a predetermined voltage level to complete a connection to the shared equipment, the status indication circuit comprising: an input terminal for connection to at least one access circuit; a switching circuit connected to the input terminal, providing a first output potential at a first voltage level, which is greater than the predetermined voltage level, when fewer than two access circuits are connected to the input terminal; an output terminal for connection to the switching means in the access circuit; resistive means connected between the switching circuit and the output terminal, responsive to the connection of an access circuit to the output terminal to produce a voltage drop and thereby to reduce the potential at the output terminal to a second voltage level, which is less than the predetermined voltage, and breakdown means connected in parallel with the resistive means, the breakdown voltage of the breakdown means thereby controlling the voltage difference between the first voltage level and the second voltage level.

Claim 9

In a telephone system, a status indication circuit for indicating the busy-idle condition of shared call processing equipment to an access circuit attempting to complete a connection to the shared equipment, the access circuit having switching means responsive only to a voltage level which is greater than a predetermined voltage level to complete a connection to the shared equipment, the status indication circuit comprising: an input terminal for connection to at least one access circuit; a switching circuit connected to the input terminal, providing a first output potential at a first voltage level, which is greater than the predetermined voltage level, when fewer than two access circuits are connected to the input terminal; an output terminal for connection to the switching means in the access circuit; resistive means connected between the switching circuit and the output terminal, responsive to the connection of an access circuit to the output terminal to produce a voltage drop and thereby to reduce the potential at the output terminal to a second voltage level, which is less than the predetermined voltage, and breakdown means connected in parallel with the resistive means, the breakdown voltage of the breakdown means thereby controlling the voltage difference between the first voltage level and the second voltage level.

Claim 10

A status indication circuit as claimed in claim 6 further comprising: threshold circuit means connected between the input terminal and the switching circuit and being responsive to the connection of more than one access circuit to the input terminal to transmit a switching signal to the switching circuit, the switching circuit being responsive to the switching signal to develop an output potential at a third voltage level which is substantially less than the second voltage level.

Claim 11

In a telephone system, the combination of a status indication circuit for indicating the busy-idle condition of shared call processing equipment and of an access circuit for attempting in response to a request-for-service signals, to complete a connection to the shared equipment said combination comprising: the access circuit including first switching means responsive only to a voltage level which is greater than a predetermined voltage level to complete the connection; the status indication circuit including first circuit means normally presenting a first voltage level to the access circuit when the shared equipment is idle and a second voltage level to the access circuit when the shared equipment is busy, only the first voltage level being greater than the predetermined voltage level, and second circuit means respoNsive to a completed connection for controlling the difference between the first voltage level and the second voltage, and the access circuit further including second switching means responsive to the request for service signal for transmitting a signal, which is independent of the first switching means to the status indication circuit as soon as the first switching means initially responds to a first voltage level to complete the connection, the transmitted signal causing the first circuit means to present a second voltage level to the access circuit.

Claim 12

In a telephone system, the combination of a status indication circuit for indicating the busy-idle condition of shared call processing equipment and of an access circuit for attempting in response to a request-for-service signals, to complete a connection to the shared equipment said combination comprising: the access circuit including first switching means responsive only to a voltage level which is greater than a predetermined voltage level to complete the connection; the status indication circuit including first circuit means normally presenting a first voltage level to the access circuit when the shared equipment is idle and a second voltage level to the access circuit when the shared equipment is busy, only the first voltage level being greater than the predetermined voltage level, and second circuit means respoNsive to a completed connection for controlling the difference between the first voltage level and the second voltage, and the access circuit further including second switching means responsive to the request for service signal for transmitting a signal, which is independent of the first switching means to the status indication circuit as soon as the first switching means initially responds to a first voltage level to complete the connection, the transmitted signal causing the first circuit means to present a second voltage level to the access circuit.

Claim 13

The combination as claimed in claim 8 wherein the status indication circuit further comprises: second circuit means responsive to substantially simultaneous attempts by more than one access circuit to complete a connection to the shared equipment to override the first circuit means and to present a third voltage level, which is less than the second voltage level, to the access circuits.

Claim 14

The combination as claimed in claim 8 wherein the access circuit further comprises: an input terminal for receiving a request-for-service pulse and pulse shaping circuit means connected to the input terminal; the second switching means comprises first and second four layer diodes having first and second firing voltages, respectively, the magnitude of one of the firing voltages being greater than the magnitude of the other of the firing voltages, and each being arranged to select a different piece of shared equipment, and the pulse shaping circuit being operative to shape a pulse applied to the input terminal into a ramp-shaped wave which is applied to the four layer diodes, the four layer diode having the smaller firing voltage thereby being permitted to fire and to definitively select an idle piece of shared equipment before the other four layer diode fires.