Cross-point switching arrangements including triggerable avalanche devices

Claim 2

A cross-point switching circuit for a telephone line comprising: first and second input terminals connected to a telephone line; first and second alternating current coupling circuits, eacH including a direct current path; first and second triggerable avalanche devices; first and second power terminals for connection to opposite polarity terminals of a source of unidirectional energizing potential; circuit means connecting the main terminals of said first device and said first coupling circuit in a direct current series circuit between said first input terminal and said first power supply terminal; circuit means connecting the main terminals of said second device and said second coupling circuit in a second direct current series circuit between said second input terminal and said second power terminal, and switching circuit means for applying a switching signal to the gate electrodes of said first and second devices for rendering said devices conductive in response to an off hook condition in said telephone line to provide a direct current series circuit between said telephone line and said power terminals, including said coupling circuits, and to apply the unidirectional potential to said telephone line.

Claim 3

A cross-point switching circuit as defined in claim 1 including means for isolating the gate electrodes of said devices to block current flow therethrough after said devices are conductive and said switching signal is removed.

Claim 4

A cross-point switching circuit as defined in claim 2 wherein: said avalanche device is a silicon control rectifier; said isolating means includes a separate diode in series with each of said gate electrodes and means for back-biasing said diode, and said switching circuit means provides said switching signal by forward biasing said diode.

Claim 5

A cross-point switching circuit as defined in claim 1 wherein each of said avalanche devices are Triacs.

Claim 6

A cross-point switching circuit as defined in claim 4 wherein said switching circuit means includes a pair of auxiliary Triacs, a separate auxiliary Triac for each of said first and second Triacs, each auxiliary Triac having one main terminal connected in series with a separate one of said Triac gate electrodes, and circuit means connected to the other main terminal and gate electrode of said auxiliary Triacs for rendering said auxiliary Triacs conductive and nonconductive.

Claim 7

An electrical circuit for a telephone line comprising: a pair of input terminals for connection to a telephone line; a pair of triggerable avalanche semiconductor devices, each including a pair of main terminals defining a bidirectional current path therebetween and a gate electrode for rendering said path conductive; signal circuit means including a direct current path for providing a periodic signal having sufficient amplitude for actuating a telephone ringer; a pair of power terminals for connection to opposite polarity terminals of a source of unidirectional energizing potential; circuit means connecting the main terminals of one of said pair of semiconductor devices in a direct current series circuit between one of said pair of input terminals and one of said power terminals; circuit means connecting the main terminals of the other one of said pair of semiconductor devices in a direct current series circuit between the other one of said input terminals and the other one of said power terminals; circuit means for connecting the direct current path of said signal circuit means in at least one of said series circuits, and switching circuit means for applying a signal to said gate electrodes of said first and said second semiconductor devices to render said devices conductive thereby providing a current path for applying said periodic signal and the unidirectional potential to said telephone line.

Claim 8

An electrical circuit for a telephone line comprising: a pair of input terminals for connection to a telephone line; a pair of triggerable avalanche semiconductor devices, each including a pair of main terminals defining a bidirectional current path therebetween and a gate electrode for rendering said path conductive; signal circuit means including a direct current path for providing a periodic signal having sufficient amplitude for actuating a telephone ringer; a pair of power terminals for connection to opposite polarity terminals of a source of unidirectional energizing potential; circuit means connecting the main terminals of one of said pair of semiconductor devices in a direct current series circuit between one of said pair of input terminals and one of said power terminals; circuit means connecting the main terminals of the other one of said pair of semiconductor devices in a direct current series circuit between the other one of said input terminals and the other one of said power terminals; circuit means for connecting the direct current path of said signal circuit means in at least one of said series circuits, and switching circuit means for applying a signal to said gate electrodes of said first and said second semiconductor devices to render said devices conductive thereby providing a current path for applying said periodic signal and the unidirectional potential to said telephone line.

Claim 9

An electrical circuit as defined in claim 6 wherein said pair of triggerable avalanche semiconductor devices are Triacs.

Claim 10

An electrical circuit as defined in claim 7 including means for connecting an alternating current coupling circuit in at least one of direct current series circuiT for providing an output communications signal path for said telephone line.