Key telephone system signaling circuit

Claim 2

In a key telephone set circuit having a line lamp, a signaling conductor, a unidirectional conducting device in series with said lamp and said conductor, and means applying successive signals to said conductor, said signals energizing said lamp to an illuminated state, the improvement comprising a line pickup key including means operable for electrically bypassing said device to supply a supervisory signal to said conductor during the interval between said successive energizing signals, and a resistive network connected between a source of negative and positive potentials, said network being connected to said signaling conductor for rendering said device nonconductive and to receive said supervisory signal.

Claim 3

The key telephone set circuit in accordance with claim 1 further comprising means responsive to said supervisory signal foR generating a functional output signal indicative of the actuation of said bypassing means.

Claim 4

The key telephone set circuit in accordance with claim 2, wherein said generating means comprises, a supervisory relay, a relay driver activatable for operating said relay, and gating means responsive to said supervisory signals for activating said relay driver.

Claim 5

The key telephone set circuit in accordance with claim 3, wherein said unidirectional conducting device consists of a diode.

Claim 6

The key telephone set circuit in accordance with claim 4, wherein said bypassing means includes a contact of said line pickup key.

Claim 7

The key telephone set circuit in accordance with claim 5, wherein said applying means includes a plurality of relay devices having a plurality of contacts, and a transistor gating arrangement having an output connected to said supervisory conductor, said gating arrangement having an input connected to a configuration of said contacts for supplying a plurality of selectable lamp energizing signals to said supervisory conductor.

Claim 8

A key telephone circuit, a line lamp having a first and a second terminal, a first source of potential, a diode connecting said first terminal and said first potential source, a second source of potential resistively connected to said second terminal, said second potential being of the same polarity but of higher magnitude than said first potential, and said diode being poled to prevent current flow between said first and said second sources of potential, a line pickup key operable to shunt said diode and and apply said first potential through said lamp to said second terminal to shunt down said second source of potential, driver means applying successive signals to said second terminal for steadily illuminating said lamp, and means connected to said second terminal for detecting a change in potential on said second terminal during the interval between successive energizing signals.

Claim 9

A key telephone circuit, a line lamp having a first and a second terminal, a first source of potential, a diode connecting said first terminal and said first potential source, a second source of potential resistively connected to said second terminal, said second potential being of the same polarity but of higher magnitude than said first potential, and said diode being poled to prevent current flow between said first and said second sources of potential, a line pickup key operable to shunt said diode and and apply said first potential through said lamp to said second terminal to shunt down said second source of potential, driver means applying successive signals to said second terminal for steadily illuminating said lamp, and means connected to said second terminal for detecting a change in potential on said second terminal during the interval between successive energizing signals.

Claim 10

A key telephone circuit in accordance with claim 7 wherein said detecting means includes a third source of potential, voltage divider means connected between said third potential source and said second terminal, said divider means having a third terminal, and logic means having a first input connected to said second terminal and a second input connected to said third terminal for detecting a prescribed electrical condition on said second terminal.

Claim 11

A key telephone line circuit for use in a key telephone system in which successive lamp energizing signals are sent over a single conductor to a key telephone station set lamp connected in series with a unidirectional conducting device thereat and in which a supervisory signal originated at the set is returned over said conductor by short-circuiting said device resulting in rendering said device nonconductive while short-circuited and resulting in the application of said supervisory signal to said conductor during the intervals between said successive signals, said line circuit comprising a resistive network connected between a first and a second source of potential and having a first and a second junction, said first junction of said network being connected to said conductor via a single connection thereto for receiving said supervisory signal, and means connected to both said first and said second junction for detecting said supervisory signal.

Claim 12

A key telephone line circuit for use in a key telephone system in which successive lamp energizing signals are sent over a single conductor to a key telephone station set lamp connected in series with a unidirectional conducting device thereat and in which a supervisory signal originated at the set is returned over said conductor by short-circuiting said device resulting in rendering said device nonconductive while short-circuited and resulting in the application of said supervisory signal to said conductor during the intervals between said successive signals, said line circuit comprising a resistive network connected between a first and a second source of potential and having a first and a second junction, said first junction of said network being connected to said conductor via a single connection thereto for receiving said supervisory signal, and means connected to both said first and said second junction for detecting said supervisory signal.

Claim 13

A key telephone station set arrangement for use in a key telephone system in which successive station set lamp signals and a supervisory signal are multiplexed on a single conductor connecting a station set to key telephone equipment comprising a station set line lamp connected to said single conductor, a source of supervisory signal at said station set, a unidirectional conducting device connecting said lamp and said source of supervisory signal, said device being connected to block said source of supervisory signal from said lamp and said conductor, a line pickup key at said station set, and means responsive to the operation of said key for short-circuiting said device to render said device nonconductive while said key is operated and wherein said short-circuiting means also applies said source of supervisory signal to said conductor.

Claim 14

A key telephone station set arrangement for use in a key telephone system in which successive station set lamp signals and a supervisory signal are multiplexed on a single conductor connecting a station set to key telephone equipment comprising a station set line lamp connected to said single conductor, a source of supervisory signal at said station set, a unidirectional conducting device connecting said lamp and said source of supervisory signal, said device being connected to block said source of supervisory signal from said lamp and said conductor, a line pickup key at said station set, and means responsive to the operation of said key for short-circuiting said device to render said device nonconductive while said key is operated and wherein said short-circuiting means also applies said source of supervisory signal to said conductor.