Miniature Intercommunication Key Telephone System (Patent No: 861628)

Inventor: Cartwright, Delmar G.

Location: Edmonton

Comments: N/A

Description: 1. A key telephone system having an intercommunication circuit including a common talking path shared by a plurality of subscriber stations, multi-bank switch means operated responsive to dial pulses from subscriber stations for selectively signalling individual ones of said subscriber stations, means comprising a combination of electronic and electro-mechanical devices for controlling said switch means responsive to dial pulses from subscriber stations, transistor means for distinguishing dial pulses and short duration pulses attributable to jiggling of a hook switch at a subscriber station, said transistor means being biased by delaying means to be switched only responsive to a pulse of a minimum predetermined length, means responsive to said transistor means being switched for driving said switch means to select a station responsive only to said dial pulses, signal current transmitting means for transmitting a signal current through at least one of the multi-bank switch means to the subscriber station selected by said dial pulses, said signal current transmitting means comprising means for transmitting any selected one of many different forms of signalling current through a selected terminal in said one bank, means for transmitting a different one of said many signalling currents through another bank of said switch means, means responsive to the answer by the party at the selected station for sending answer supervision signals through a second of said banks, and means responsive to said answer supervision signals for terminating the transmission of said signalling current through said one bank.

2. The system of Claim 1, and means whereby said answer supervision responsive mean terminates all of said signaling currents.

3. The system of Claim 2, and a second multi-bank switch means, means utilizing said combination of devices for driving said first mentioned switch means responsive to the receipt of a first train of dial pulses, and means also utilizing said combination of devices for driving a second switch means responsive to the receipt of a second train of dial pulses.

4. The system of Claim 3, further comprising means responsive to said first train of dial pulses for driving said first mentioned switch means to signal either anyone of nine subscriber stations or to change over the said second switch means, and means responsive after said change over to said second train of dial pulses for driving said second switch means to signal any one of ten additional subscriber stations.