Contents

How telephones began

How Edison improved on the early telephone

How the sound of your voice travels

Sound waves into electric currents

The Transmitter

The Receiver

Telephone exchanges

Manual exchanges

Automatic exchanges

How the selectors work

Automanual switchboards

Dialling codes

Exchange systems

Long distance telephoning

Helping the electric currents over long distances

International services

Radio-telephones

The Post Office Tower

Telephoning by Satellite

Special services

Emergency services

Public services

Learning more about the telephone

Vocabulary