Question - What is a transducer and transponder?
Answer -
A transducer is a device, usually electrical, electronic, electromechanical, electromagnetic, photonic, or photovoltaic that converts one type of energy or physical attribute to another for various purposes including measurement or information transfer. In telecommunication, the term transponder (short for Transmitter responder and sometimes abbreviated to XPDR, XPNDR, TPDR or TP) has the following meanings:
An automatic device that receives, amplifies, and retransmits a signal on a different frequency (see also broadcast translator).An automatic device that transmits a predetermined messagein response to a predefined received signal. A receiver transmitter that will generate a reply signal upon proper electronic interrogation. A communications satellite’s channels are called transponders, because each is a separate transceiver or repeater.