H - Electricity – 04 – M
Patent
H - Electricity
04
M
379/30
H04M 1/00 (2006.01) H04M 11/04 (2006.01)
Patent
CA 1145077
CIRCUIT FOR INTERFACING NON-DIAL TELEPHONE AND AUTOMATIC SWITCH EQUIPMENT ABSTRACT OF THE DISCLOSURE A ring-down or non-dial subscriber telephone such as a freeway emergency telephone is connected to automatic electronic switching (EAX) equipment for interconnection with an emergency operator by an interface circuit having a polarity-sensitive full wave bridge controlling voice connection of the tele- phone to the operator. Actuation of the bridge is controlled by a current sensitive controller connected in series with the originating loop containing the freeway telephone. The bridge monitors the on-hook and off-hook states of the called telephone and ener- gizes alarm circuitry upon failure of the calling telephone to go on-hook within a predetermined tome after the called telephone goes on-hook. The circuit also has an isolating photo-coupled switch for mon- itoring current flow in the originating loop containing the calling telephone and for energizing a common alarm circuit in the EAX equipment in the absence of such current flow. A relay circuit is also pro- vided for disconnecting the interface circuit from the common alarm system while retaining identification of the calling telephone responsible for the alarm condition.
348759
Lodas Gregory W.
Stewart Dennis M.
Gte Automatic Electric Laboratories Incorporated
R. William Wray & Associates
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