Rotary discharger, part of spark radio transmitter; made by Amalgamated Wireless Australasia Ltd. for use in the Marconi Telefunken System for ship-to-shore and ship-to-ship radio communication.

The device is connected between a capacitor and an inductor. The capacitor is charged to a high voltage from a alternating current source, such that the gap will break down causing a spark to cross from one copper electrode to the other via a toothed wheel. The gap is adjusted such that the gap breaks down when the spacing is close to the minimum. The wheel is driven by a motor (missing). As the wheel rotates, the spark is interrupted to produce an audible tone in the transmission. A morse code message is produced by keying the spark on and off producing a series of tones (the dots and dashes of morse code).

Physical Description

Metal and ebonite device on wooden table on wooden base. Wooden table top and base have elliptical holes ( to allow connection to motor (missing) via a belt (missing). Device consists of a toothed wheel on an axle with pulley at other end. The wheel lies between two adjustable electrodes mounted on ebonite blocks, which are connected to terminal screws mounted on ebonite cylinders. The electrodes show darkening and erosion due to use.

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