US 4,149,040 A · Identifier circuit for identifying party line subscribers

Abstract

An identifier circuit for connection between a telephone system party line and a party line subscriber to permit identification of a calling party line subscriber with automatic number identifying equipment at a central office. The identifier circuit includes a pair of terminals adapted to be selectively connected to ground in accordance with identification of a particular party line subscriber, a pair of normally nonconductive test transistors each connected between one of the terminals and one of the leads of the party line, a pair of control transistors responsive to voltage on the party line to maintain the test transistors nonconductive and responsive to removal of the party line voltage to permit the test transistors to conduct, and a pair of capacitors charged when a calling subscriber goes off hook and discharged to maintain the test transistors conductive for a predetermined time during which testing of the party line to identify the calling subscriber can be accomplished with automatic number identifying equipment at the central office.

Claims15

Dependent claims

An identifier circuit for connection between a telephone system party line and a party line subscriber comprising

bus means for connection with the party line;
a reference potential terminal;
and
time control means connecting said reference potential terminal to said bus means for a predetermined time after voltage is removed from the party line in response to the party line subscriber going off hook whereby said party line identifier circuit can be tested to identify a calling party line subscriber during said predetermined time, wherein expiration of said predetermined time is marked by restoration of said party line voltage.

1 more element

An identifier circuit for connection between a telephone system party line having first and second leads and a party line subscriber comprising

a first bus adapted to be connected with the first lead of the party line;
a second bus adapted to be connected with the second lead of the party line;
first and second terminals adapted to be connected with a reference potential in accordance with the identification of a particular party line subscriber;
first test switch means connected between said first terminal and said first bus and having a normally nonconductive state and a conductive state;
second test switch means connected between said second terminal and said second bus and having a normally nonconductive state and a conductive state;
control switch means connected with said first and second buses and said first and second test switch means and responsive to voltage on the party line to be in a first state to maintain said first and second test switch means in said nonconductive states or in a second state permitting said first and second test switch means to be placed in said conductive state;
and
biasing means connected with said first and second buses and operative to place said first and second test switch means in said conductive states for a predetermined time whereby testing of said party line to identify the party line subscriber can be accomplished during said predetermined time by applying test voltages to the party line to determine the connection of said first and second terminals with the reference potential.

5 more elements

Dependencies are inferred from the claim text.

Identifier circuit for identifying party line subscribers

Life of this patent

Identifier circuit for identifying party line subscribers

Life of this patent

Abstract

Claims15