To ensure the delivery of the correct information to the correct recipient, the signals that have been received must be separated, demodulated and routed to the appropriate telephone line. As mentioned briefly already, the receiver relies on a synchronisation pulse to initiate the separation process at the receiving end. This signal is of significantly longer duration (in electrical terms) than the channel pulses and is received by the aerial mounted on the roof of the receiver station. A train of these signals can be seen in the diagram.

From here, the signal is communicated to an oscillator which contains a crystal detector that converts the wave energy into electrical signal. A saw-tooth pulse corresponding to the original channel pulse is generated. The separator unit uses a system of gates that relate to the number of channels available, in this case eight. The pulses are superimposed on a monitor, a cathode ray tube to allow the operator to position the gates in an accurate position over the related pulse. Click on the speaker to listen to Trevor Ramm’s response to the use of a cathode ray tube in the WS10.

The gates are timed to coincide with the time duration of their corresponding pulse and so discriminate against data being transmitted on other channels. The diagram on the right illustrates how the electrical pulse is ‘captured’ by the gate before the following pulse is able to cause signal interference. Though each channel transmits its data in rapid succession, the separator uses the synch pulse to determine when to open and when to close the appropriate gate; each gate only opens once per cycle, barring all the pulses that lie outside this band. The modulated electrical pulse can now amplified and routed to the appropriate telephone line.