Telephone exchange
device · 1878 · Electric age
Switching subscribers; manual, then automatic.
What it is made of
- Strowger switch — has part. Automatic selectors.
- Relay — has part. Relay switching.
Principles and materials it uses
- Copper — is made of. Switchboards are copper wires.
Where it is used
- Telephone — is used in. Connecting subscribers.