Useful for the demonstration of characteristics associated with high voltage phenomena such as with Geissler tubes, spectrum analysis tubes etc. This traditional induction coil is capable of producing a spark length of up to 30mm with an input of 6 to BV DC and is therefore ideal for use with vacuum tubes, eudio meters, etc. A fully adjustable trembler system is incorporated and spark suppression capacitors are housed in the base.Ruhmkorff commutator allows primary current to be both reversed and switched ON/ OFF with make-and-breakpoint. A pair of pointed electrodes is supplied with the instrument, the pointed electrodes having an insulating handle for adjustment of the spark gap. Low voltage input is via a pair of baseboard mounted colour coded 4mm sockets.