Induction coil; '10 inch' type. Used in Marconi radio equipment for shipboard operation. Made by Amalgamated Wireless (Australasia) ltd, in Australia in 1918.

This type of coil was normally used for the emergency transmitter in ships. It could be run from the ship's emergency battery because it did not need much power. Normal transmission required the ship's main power supply to run the rotary converter and discharger. The coil shares the wooden base with the spark gap, namely, two insulating poles holding two spheres across an adjustable gap. When in emergency use, one side of the gap is connected to earth and the other is connected to the aerial tuned circuit. This produces a very poor quality signal, but better than nothing in an emergency.

Use of this device for 'normal' operation was frowned on because an induction coil based transmitter produced a signal, which covered a broad spectrum of frequencies, which would interfere with other communications. However, in emergencies, this broad signal was more likely to be noticed by other ships compared with the cleaner signal of the main transmitter.

Physical Description

Large black cylinder in wooden base with various contols, connections and reminals. I front, there are two vertical pillars, each with a horizontal pin. The poits of the two pins face each other across a gap.

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