Method and apparatus for automatically identifying an individual calling party on a multiparty telephone line

An automatic party identifier useful in conjunction with and forming part of an apparatus for detecting which party on a multiparty telephone line has placed a call thereon, said automatic party identifier comprising:

• (a) a voltage source;
• (b) means for selectively interconnecting said voltage source with the telephone line when party identification is to be made to thereby apply to the telephone line a voltage having a magnitude sufficient to produce a first predetermined value of loop current therein;
• (c) means for regulating loop current in the telphone line at said first predetermined value, and for alternately regulating the magnitude of the voltage applied to the telephone line by said voltage source at said magnitude sufficient to produce said first predetermined value of loop current therein;
• (d) timing means for producing a plurality of timing signals, a first one of said plurality of timing signals controlling said regulating means so that said regulating means regulates said loop current for a predetermined period of time sufficient to stabilize said loop current at said first predetermined value, and so that said regulating means thereafter regulates the magnitude of said voltage applied to the telephone line;
• (e) current level detector means providing a current level signal representative of said loop current;
• (f) threshold means responsive to a second one of said plurality of timing signals to compare, at a time subsequent to said predetermined period of time, said current level signal with a threshold value of said loop current, said threshold value being lower than said first predetermined value, but higher than a second predetermined value which is greater than the value of said loop current that would signify an on-hook condition on the telephone line, said threshold means providing an output signal when said loop current equals or exceeds said threshold value;
• (g) decoder means responsive to a third one of said plurality of timing signals to provide a plurality of successive signals each existing during succeeding time intervals, each succeeding time interval being unique to one of the parties on the multi-party telephone line, and
• (h) output means responsive to concurrence of said output signal from said threshold means and one of said successive signals to provide a party identification signal.

A subscriber module useful in conjunction with and forming part of an apparatus for detecting which party on a multiparty telephone line has placed a call thereon, said subscriber module including:

• (a) first and second terminals adapted to be connected in series circuit with the telephone line;
• (b) first means connected between said first and second terminals for shunting current therebetween in a first predetermined direction of said current;
• (c) second means connected between said first and second terminals for controlling current therebetween in a second direction of said current which is opposite to said first direction, said second means including:
• (i) timing means responsive to the detection of current in said second direction for providing a pluraity of successive timing signals,
• (ii) current regulating means for regulating the magnitude of said current in said second direction at a predetermined value which is greater than the magnitude of said current that would signify an on-hook condition on the telephone line, said current regulating means initiating said current regulation in response to a first one of said plurality of timing signals and terminating said current regulation in response to a second, subsequent one of said plurality of timing signals, and
• (iii) means selectively shunting current between said first and said second terminals in said second direction in response to said second one of said plurality of timing signals.

A subscriber module useful in conjunction with and forming part of an apparatus for detecting which party on a multiparty telephone line has placed a call thereon, said subscriber module including:

• (a) first and second terminals adapted to be connected in series circuit with the telephone line;
• and
• (b) means connected between said first and second terminals for controlling current therebetween in a predetermined direction of said current, said means including:
• (i) timing means responsive to the detection of current in said predetermined direction for providing a plurality of successive timing signals,
• (ii) current regulating means for regulating the magnitude of said current in said predetermined direction at a predetermined value which is greater than the magnitude of said current that would signify an on-hook condition on the telephone line, said current regulating means initiating said current regulation in response to a first one of said plurality of timing signals and terminating said current regulation in response to a second, subsequent one of said plurality of timing signals, and
• (iii) means selectively shunting current between said first and said second terminals in said predetermined direction in response to said second one of said plurality of timing signals.

An apparatus for providing, at a central office, a party identification signal identifying that one of a plurality of party stations, interconnected with a telephone line, from which a telephone call has been placed, and wherein the central office includes means for providing an enabling signal in response to the detection of placement of a call on the telephone line and for removing the enabling signal upon provision of said party identification signal, said apparatus comprising:

• (a) an automatic party identifier for location at the central office;
• (b) means interconnecting said automatic party identifier with the telephone line in response to and for the duration of said enabling signal;
• (c) first means within said automatic party identifier for applying to the telephone line a voltage having a magnitude sufficient to produce a first predetermined value of loop current in the telphone line;
• (d) a plurality of subscriber modules, each of said plurality of subscriber modules being adapted to be located in circuit with one of said plurality of party stations in the telephone line and responding to said voltage by initially regulating the value of said loop current at a second predetermined value, said second predetermined value being smaller than said first predetermined value but being greater than the value of said loop current that would signify to the central office that an on-hook condition exists on the telephone line, and by subsequently terminating said regulation after the passage of a predetermined time from the application of said voltage, said predetermined time being unique to that one party station, whereby the value of said loop current rises from said second predetermined value toward said first predeterined value;
• (e) second means within said automatic party identifier for providing an output signal when the value of said loop current equals or exceeds a threshold value intermediate said first and said second predetermined values thereof;
• (f) third means within said automatic party identifier which is responsive to said first and seond means thereof for providing said party identification signal identifying a particular one of said plurality of party stations upon concurrence of said output signal and any one of a plurality of predetermined time intervals, each said predetermined time interval being subsequent to the application of said voltage and being unique to and therefore representative of one of said party stations.