Method of transmitting messages with predetermined message duration from batteryless transponders to interrogation devices circuit of a radio transmitter-receiver

Abstract From the Canadian patent

A method is described with the aid of which messages can be transmitted from batteryless transponders to interrogation devices. The interrogation devices are equipped with a receiving section and a transmitting section arid as a request to transmit the message stored therein as reaction to an interrogation command rendered effective in the interrogation device said devices transmit an HF interrogation pulse with predetermined carrier frequency and predetermined carrier duration. In the transponder this HF interrogation pulse is utilized to generate a supply voltage. Each interrogation device checks as reaction to an interrogation command whether its receiving section (14) is receiving a …