the generator then preferably is impressed on a phase modulating diode in a frequency converter as a result the frequency converter emits to the antenna 220 a sideband that is provided with a code corresponding to the coded sawtooth shaped signal the sideband signal is fed to antenna 220 from which it is re emitted to the reading device 235 upon reception of the coded sideband signal the reading device 235 decodes it and processes it further to recover the transmitted information the information stored in the memory of the transceiver 215 may be an identification code that identifies and is individual to the particular instrument in which the transceiver is implemented or attached to thus the sideband signal transmitted from the transceiver 215 in response to the reception of the interrogating signal 240 will contain the stored identification code the identification code or other information that is stored in the memory is to be distinguished from the key code which is stored in key means as will be appreciated by those skilled in the art the key code may be the same for a large number of transceivers e g instrument trays and medial and or surgical instruments in the overall communication system because the purpose of the key means is to prevent the memory from being keyed i.