Transducer

A transducer is a device, usually electrical, electronic, or electro-mechanical, that converts one type of energy to another for the purpose of measurement or information transfer. Most transducers are either sensors or actuators. ...

とりあえず「センサとアクチュエータの総称」と覚えておけばいいか？ そう言っちゃうと液晶ディスプレイや発光ダイオードは含まれないけど...