Telephone interface circuit

• US 20070025549A1
• Filed: 07/06/2005
• Published: 02/01/2007
• Est. Priority Date: 07/06/2005
• Status: Abandoned Application

• Current Assignee: Uniden Corporation (Cornwall Capital Management LP)
• Original Assignee: Uniden Corporation (Cornwall Capital Management LP)
• Inventors: Fujiwara, Yoshinobu
• Application Number:
  US11/175,944
• Publication Number:
  US 20070025549A1
• Time in Patent Office: Days
• US Class Current: 379/412
• CPC Class Codes: H04M 1/745 Protection devices or circuits for voltages surges on the line

Abstract

A telephone interface circuit includes a speech circuit, a hook switch that opens and closes connection between a subscriber line and the speech circuit, an overvoltage detector that detects overvoltage input to the subscriber line, and a control circuit that controls the hook switch when overvoltage is detected by the overvoltage detector so as to open the connection between the subscriber line and the speech circuit.

Claims

1. A telephone interface circuit comprising:

a speech circuit;

a hook switch opening and closing a connection between a subscriber line and said speech circuit;

an overvoltage detector detecting overvoltage that is input to said subscriber line; and

a control circuit controlling said hook switch when the overvoltage is detected by said overvoltage detector, so as to open the connection between said subscriber line and said speech circuit.

2. The telephone interface circuit according to claim 1, wherein said control circuit is an SCR circuit that turns off said hook switch in response to trigger voltage output from said overvoltage detector.

3. The telephone interface circuit according to claim 1, wherein said control circuit closes the connection between said subscriber line and said speech circuit after a lapse of a predetermined time from opening of the connection between said subscriber line and said speech circuit.

4. The telephone interface circuit according to claim 3, wherein said control circuit is a monostable multi-vibrator that turns off said hook switch in response to trigger voltage output from said overvoltage detector.

5. The telephone interface circuit according to claim 1, wherein said overvoltage detector is provided between said speech circuit and said hook switch.

6. The telephone interface circuit according to claim 1, wherein said hook switch is a transistor element.