Full Details

Name and Model Number "The Electrician" PRACTICAL
Country of Origin England
Date of Manufacture est. 1911
Front Scales Upper stock: Frequency per 1/1000 sec Wavelength in 1000 feet Wavelength in 1000 metres. Labelled C but in traditional A position. Red circled gauge marks ‘A and ‘B’ the latter at 2pi used for reading results.
Slider: Wavelength – in 1000 metres labelled D to match C. Capacitance in Micromicrofarads x 100 = 90 cms Micromicrofarads in 100 cms Lower stock: Inductance in Microhenries x 10 20 cm scale.
Back Scales No scales. ‘Instructions for Use.’ Various equations. Tables for wavelength conversion, dielectric constants and spark gap length/voltage.
Scale Length 19.9 cm, with overall size 25.2 cm x 6.8 cm
Type of Rule Slide Rule
Construction Coated stiff cardboard
Area of Use Electrical
Comment 1) Electrical – L, C, wavelength and frequency for tuned circuits in spark gap transmitters used in wireless telegraphy.
Instructions on reverse note that the C and D scales can also be used for ordinary calculating.
2)The designer Henry Richard Belcher-Hickman M.A. M.B. is well documented as working in medicine. His electrical interests are described in V J Phillips ‘Early radio wave detectors’, 1978, p.199.
3)An owner’s name ‘Percival J. Parmiter’ is handwritten on reverse of slider. A person of this name ‘P. J. Parminter’ (sic) is on record in Gamage’s ‘Directory of Amateur Wireless Stations’ 1913 as operating a 35W transmitter in Bournemouth with call letters PXH. He presented talks on wireless telegraphy and other related subjects at the Bournemouth Natural History Society.
Rarity RRR
Donor Collection of David Walker, Huddersfield, UK
Match Number 401
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In conjunction with our 'donors' we assign a rarity rating to each item, based on the system devised by Herman van Herwijnen
(1929 - 2004), renowned Dutch collector, author, and creator of Herman's Archive, a collection of 5,000 slide rule images on CD.
• RR = Rare - 1 of 25 collectors has one; it may take a year to find an example in the marketplace.
• RRR = Very Rare - only a few known to collectors; may be several years before it comes up for sale.
• RRRR = Extremely Rare - a museum piece; unlikely that an example will come up for sale.