|Name and Model Number||"The Electrician" PRACTICAL |
WIRELESS SLIDE RULE
|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.
|Donor||Collection of David Walker, Huddersfield, UK|
(Click Picture for Details)
|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.|