Automatic telephone location system

Claim 1

An automatic telephone location system fOr determining the location or address of telephones used in making calls to telephones at certain stations in automatic telephone systems having a plurality of telephones connected by telephone networks through a central office or the like, comprising, a plurality of first telephones connected to a telephone network, a second telephone located at a second station and being connected to the telephone network, storage means at each of said first telephones for storing a coded address representing the location of the particular first telephone, interrogating signal means at said second telephone for sending an interrogation signal to said first telephone in response to a telephone call from said first telephone to said second telephone, detector means at said first telephone for detecting and receiving said interrogation signal and activating said storage means to send out a signal to said second telephone that is coded to the address of said first telephone, receiver means at said second telephone for receiving said address coded signal and decoding said address coded signal to identify the location of said first telephone, said storage means at said first telephones including a programmed memory unit, clock signal means for interrogating said programmed memory unit, tone generator means for generating serial two tone output signals of binary coded address information that are coded by signal outputs from said programmed memory unit, said receiver means including a tone detector means for detecting the difference between serially received serial tones, an address detector means for detecting the output of said tone detector means providing decoded address output signals corresponding to the address of the first telephones, means for displaying or storing the received decoded address output signals, said detector means including filter means for filtering a signal having the particular frequency of the interrogating signal, threshold detector means for receiving a signal from said filter means, said clock signal means including oscillator means for providing clock signals in response to an output signal from said threshold detector means, said program memory unit providing a digital output signal upon being interrogated by said clock signals, said digital output corresponding to the individual components of the address of the first telephones, and second oscillator means for providing a first frequency for a given digital signal of said digital output and a second frequency for a second digital signal of said digital output providing said two-tone output signal of binary coded addressed information.