Virtual Science Museum

Miscellaneous Items

This is a totally bizarre electromechanical indicator device made by Dowty. It uses four triangular sections which are rotated by a rack arrangement. The indicator normally displays the red up arrow, but when either of two electromagnets are energized, the triangles rotate to display one of the other two legends.

This hand crafted box is labelled 'The Cox-Cavendish Electrical Co. Ltd. X-Ray & Electro-Medical Apparatus'. It appears to contain an induction coil. I tried connecting it to a dc supply and it started making a threatening noise rather like a rattle snake. It is almost certainly a faradic medical battery, used for muscular therapy.

This is an early digital component which they called a logical circuit element. This device is a monostable.

50 pence piece for scale.

This is a 100kHz crystal oscillator module. The crystal is in the glass tube. It was made by Venner Electronics Limited and contains germanium transistors. The module is potted in solid plastic. It measures 125mm high including the pins.

Place your pointer over the picture to see an X-Ray of the module. Dark areas are low density and light areas are high density.The rectangle, top center, appears to be a mica capacitor. The large white discs are probably ferrite cored inductors or transformers. The three small white tubes on the right are germanium transistors.

Ediswan DLS10 time delay switch.

A 4V filament on the right heats a bi-metallic strip. After a delay of about one minute, the bi-metallic strip bends sufficiently to close the contacts at the top of the device. It is evacuated and contains a getter.

The switch has a standard BVA 4 pin valve base. It was used in a Hirst welding set. The welder probably contained a mercury rectifier. This type of rectifier must never have HT applied without the cathode being heated. The time delay switch would have ensured that when power was applied, the cathode heated up sufficiently before HT was applied to the rectifier valve.

The switch is 116mm tall including the pins.

Ratings: Filament 4V
Delay 30s min, 90s max.
Low voltage rating 6A at 250V
High voltage rating 200mA at 1kV

Pin connections:
Pin A - Switch contact
Pin F - Filament
Pin G - Switch contact
Pin F - Filament

GEC 306 Barretter.

This is a rather unusual device which I originally mistook for an incandescent lamp. It is actually a type of regulator called a barretter.

The envelope is filled with hydrogen and contains an iron filament. The temperature co-efficient is chosen to keep the circuit current constant over a wide voltage range.

This type of device is referred to in the 1948 Ediswan data book as a 'hydrogen filled resistance lamp'.

Mystery Object!

I found this in a toolbox full of nuts and bolts. The outer housing is stainless steel. The device seems to be designed to work at high temperature because all the insulators are ceramic. Inside the tube there is a ceramic magnet which surrounds a coil. A thin ferrous rod extends from the coil into the stainless steel tube at the end of the device.

The only application I can think of is that it may have been used to detect a moving ferrous object. It may have been part of a tachometer or flow meter. Do you have any idea what it might be?