An additional ID signal representing the same ID data as the ID signal is produced based on the received time mark.

Any lag in the change of the frequency in the response signal compared to the change in the frequency of the challenge signal is indicative of the amount of delay between the challenge and response signal.

The additional ID signal is compared with the ID signal received from the communication channel.

A master node (12) transmits an identification signal to instruct a communication channel in an identification signal time slot.

Communications officer, send out a signal of identification.

The receiver processes received signals only when the identification signal received matches a reference identification signal stored in the receiver.

Then, the capsule endoscope adds the characteristic information corresponding to the identification signal (ID) after the identification signal (ID) and transmits the image information.

Communications Officer, send out an identification signal.

A field identification signal may also be generated.

On receipt of an identifying signal the called extension transmits a return signal to the calling extension, which return signal serves to terminate transmission of the identifying signal.

The identification signal generation module (600) transmits an identification signal to the control module (200) via a wired or wireless connection transmission mode.

A module transmits am identification signal to the controllert that contains an identification number of the module.

The control signal is at least partially determined from the received identifying signal.

For the receiver an identification is added to the composite signal to be transmitted.

An identification signal (IS) is transmitted from control module to control module.