Vintage SEL Induction Coil No. 1700. Spark Gap Generator

This is a quite rare British Vintage SEL Induction Coil No. 1700. Spark Gap Generator / Transmitter. A great find for all collectors of vintage technology.

In very good condition, it comes in its original brown SEL branded cardboard box with instruction leaflet (part of which is missing).

Approximate measurements:

• Base Width: 8.8 cm
• Base Length:- 10.1 cm (4")
• Height: 6 cm

This small induction coil was made by Signalling Equipment Limited (SEL) under their Merit brand: catalogue number 1700.  The base is made from blue plastic and the mounted coil is wrapped in green foil with the Merit brand logo; they are in excellent condition.

Induction coil or spark coils were used in early radio signalling testing, however, the function of this induction coil was probably not so benign. It was actually sold as a toy, and probably used by the owner to give their unwitting pets, friends and relatives electric shocks! Needless to say that this sort of 'toy' is no longer available! This version dates to the 1950s/60s.

We are selling this induction coil as a scientific curio and have deemed it unsuitable for use by children. 

Summary

• Radius cornered blue plastic base, induction coil with output wired to two metal cylinders
• Requires a 4.5 volt battery (not included). Not for mains use.
• Manufacturer SEL (Trade name for J. C. L. Randall of Potters Bar, Middlesex)
• Marked on the Box with
• SEL (Signalling Equipment Limited)
• Induction Coil

Spark Gap Transmitter and Induction Coils

A spark-gap transmitter is a device that generates radio frequency electromagnetic waves using a spark gap. This was the technology used in the first thirty years of radio transmission (1887- 1920s), using morse code, prior to the introduction of radio valves/ vacuum tubes. In order to create a spark gap you need an induction/ spark coil, (also known as an inductorium or Ruhmkorff coil after the inventor, Heinrich Rumhkorff), which produces high voltage pulses from low voltage DC.

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