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Proximity fuze - aka Variable Time or VT fuze.

The proximity fuze was designed to increase the effectiveness of artillery shells by making them explode when in the proximity of an aircraft rather than having to score an actual hit. It had in effect a miniature side-looking doppler radar built in.

See for further information.

Further information: US Patent 3166015 by Merle A. Tuve was filed in 1943 and published 22 years later. (Information provided by Chris Leyson)

Some of the valves used in these include: CV122, 2D29, 2E27

Complete unit
Top Base


Size The electronics module (left) measures 63x46mm overall including the pins - the main body is 38mm across. The one shown on the right measures 29x36mm. Proximity fuze


View of the electronics after the encapsulating wax was melted off. The three valves are all held in the centre of the circuit and the base of one is just visible top centre of the picture. Electronics
Quarter view Quarter view


The electronics module shown here has not yet been disassembled. It is different in size and construction to the other shown on this page. Proximity fuze


Size The valves measure 30x9x6mm overall. They have no markings other than one having a red spot and one a black spot. From examination the black-spot and red-spot valves appear to be pentodes, while the third valve could be a triode thyratron.


Different valves
The valves above are from a differently constructed electronics module. Each measures 31x10mm overall. Two are coded with a green spot, the other blue.


MK45 fuze A MK45 fuze (pictures courtesy of Springfield Arsenal [there used to be an ebay site associated but this has gone]) MK45 fuze
Thanks to Ed Dinning for donating some electronics modules and for allowing me to photograph his complete unit.

This file was last modified 15:30:59, Tuesday September 02, 2014