Relay
part · 1835 · Industrial Revolution
A switch operated by an electromagnet (Henry).
What it is made of
- Electromagnet — has part. An electromagnet switches the contacts.
Principles and materials it uses
- Boolean algebra — uses. Shannon showed that relay circuits implement Boolean logic.
- Copper — is made of. The winding is copper wire.
- Iron — is made of. The armature and core are iron.
Where it is used
- Electrical telegraph — is part of. Relays boosted the signal on long lines.
- Harvard Mark I — is part of. The Mark I was electromechanical, built from relays.
- Zuse Z3 — is part of. 2,600 relays.
- Turing’s Bombe — is part of. Electromechanics.
- Telephone exchange — is part of. Relay switching.
- Turn signal — is used in. A flasher relay.
- Track circuit — is part of. Track relays.
- Traffic light — is part of. Relay controllers.
- Hollerith tabulator — is part of. Relays controlled the sorting box.
History: what it evolved from and what it influenced
- Programmable logic controller — evolved into. It replaced relay cabinets.