公开(公告)号：US3587077A

公开(公告)日：1971-06-22

申请号：US3587077D

申请日：1968-08-21

Applicant: ANDREW FERDINAND KALDOR ,  LAMMERT STELLEMA

Inventor： KALDOR ANDREW FERDINAND ,  STELLEMA LAMMERT

IPC: H04H1/00 ,  H04H60/43 ,  H04H60/76 ,  H04Q9/12 ,  G08C15/12

CPC classification number: H04Q9/12 ,  H04H60/43 ,  H04H60/76

Abstract: Telemetry equipment for use in an Audience Survey System for ascertaining at a central control the program channels to which wave signal receivers are tuned at a plurality of remote preselected locations, comprising a single transmission path between the control and remote locations, an interrogation transmitter at the control center, a carrier frequency for transmission from the central control, sources of audio tones, means for grouping two or more of the tones to modulate the carrier, a different grouping of the tones being assigned to be representative of individual wave signal receivers, a transceiver at each remote location for receiving the modulated carrier, means for detecting the modulating tones thereat to initiate transmission of a reply from a respectively remote location which corresponds to the grouping of the modulating tones, means for modulating the reply signal to indicate the program to which the wave signal receiver is tuned at the remote location, and detection means at the central control for deriving from each received reply signal an indication of the tuning of the respective wave signal receiver.