The Sounder

A simple way of interpreting the received signal

The Sounder was a device for interpreting the signals coming off the telegraph cable. Every time a morse key was pressed, the sounder at the other end of the line made a corresponding 'click'.

How it worked

The sounder consisted of two electromagnets with a soft iron armature which was held a short distance away from their cores by a spring.

When a current flowed through the electromagnets a magnetic field was generated which attracted the armature. The armature then hit a small plate, creating a 'click'.

When the current stopped flowing, the spring brought the armature back up to its original position, creating the second 'click'.

This device was known as a Double Plate Sounder, since it had two separate armatures and plates. The device in its centre is a relay.

Early sounders were very quiet and what little sound they made was described as 'irritating' so later designs tried to solve these problems.

Home | Site Map