Tikker

A tikker was a vibrating interrupter used in early wireless telegraphy radio receivers such as crystal radio receivers in order to receive continuous wave (CW) radiotelegraphy signals.

In the early years of the 20th century, before modern AM or FM radio transmission was developed, radio transmitters communicated information by radiotelegraphy; the transmitter was switched off and on by the operator with a telegraph key, producing pulses of radio waves, to spell out text messages in Morse code. Around 1905 the first continuous wave radio transmitters began to replace the earlier spark transmitters. The Morse code signal of the spark transmitter consisted of pulses of radio waves called damped waves which repeated at an audio rate, so they were audible as a buzz or tone in a receiver's earphones. In contrast the new continuous wave transmitters produced a signal consisting of pulses of continuous waves, unmodulated sinusoidal carrier waves, which were inaudible in the earphones. So to receive this new modulation method, the receiver had to produce a tone during the pulses of carrier.