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Pye Electro-Devices



Pye Electro-Devices Ltd was a British manufacturer, whose product range included keyboards and keyswitches. Little is known about the organisation. Pye Electro-Devices was part of the larger Pye group of companies, which at the time that they were manufacturing keyboards, was owned by the Dutch manufacturer Philips.

There seems to be some disagreement on the history of the company. Companies House indicates that Pye T.M.C. Components Limited (registered company no. 00256980) was incorporated on the 8th of June 1931. The company changed identity numerous times over its history, becoming Pye Electro-Devices Limited in December 1977, PED Limited in December 1983, BLP Components Limited in March 1992, Belling Lee Limited in January 1994, BLP Disconnect Limited in February 2012, and finally Dialight Disconnect Limited in August 2013, before being dissolved in August 2017. The Grace’s Guide entry for the Telephone Manufacturing Co indicates that Pye made take-over bids for the Telephone Manufacturing Co (itself seemingly formed in 1915) in 1960, but did not fully take over TMC until 1976; this merged business then became (as Grace’s noted from Companies House) Pye Electro-Devices Limited in 1977. The Magnetic Devices subsidiary of Pye was merged into Pye Electro-Devices in 1977.

The Grace’s Guide entry for PED indicates that ownership of the company transferred to Cambridge Electronic Industries, before being sold off. In 1992, PED merged with Belling Lee to form BLP Components Limited, which restored the Belling Lee name in the following year. Grace’s Guide notes that the Belling Lee name was replaced by the Dialight name in 2006 (as Dialight BLP) although Companies House shows a different sequence of names to those at Grace’s Guide.

The name “PED” is used here for brevity, although the PED name did not become official until 1983.


Only one PED keyboard is known, being the “type 3” keyboard from the Acorn BBC Microcomputer. Wouter Scholten’s BBC serial numbers and dates page shows only two examples of BBC Micros with “type 3” keyboards, both appearing to have been assembled in 1984. The PED keyboard supplied for the BBC Micro used discrete mechanical switches, depicted below. The keyboard itself can be seen on Wouter’s Pictures of BBCs page. There is no branding on the PCB itself; the PED name is only documented in the DRAM Electronics Ltd catalogue, and only as the keyswitch and keycap type. It remains possible that PED only supplied the switches and keycaps, with some other firm producing the remainder of the assembly. (The keycaps themselves appear to be Comptec SS; they are not a PED product.)

Descriptions of other PED keyboard types have been encountered, but no illustrations or examples have been observed. The closest discovery is the operator’s console for the Monarch 120 Call Collect System, which uses capacitance-controlled transistor sensing with the operator’s finger as the moving portion of the capacitor. This is not a full alphanumeric keyboard, but it may be a Series 90 type, based on the description.

PED were scheduled to attend Compec ’81; the following entry was posted in the Compec ’81 Official Catalogue:

The switch and display division of Pye Electro-Devices, as an established UK manufacturer of keys and other components, is exhibiting a range of keyboards, keytops, keys, switches and displays. Featured on the stand is the new Series 84 full travel springless alphanumeric “moving diode” keyboard offering standard or custom-built units. Together with the Series 90 electronic capacitive touch keyboards.

A range of monolithic keypads for standard or waterproof applications is being shown along with the discrete keys for those building their own keyboards. These keys give a choice of mechanical contact or Hall Effect outputs and keytop styles. Also on show are panel-mounted pushbutton, thumbwheel and lever switches, as well as L.E.D. and light reflecting displays.

The News section of Electronics & Power from May 1981 contained the following article:

Whatever will key, will key

A different approach to keypad technology is the basis of a new range of products being manufactured under licence in the UK by Pye Electro Devices (PED) of Newmarket, Suffolk. Pye recently announced the deal to market and manufacture the range, designed and patented by K.Serras, the product trademark of Sigma Industries, France, at the All Electronics Show, held recently in London.

The company has spent 4 years developing a switch with magnetic return instead of the usual spring. This means that maximum force is required at the beginning of the key depression — as opposed to the end where a spring is used. Thus, it is claimed, a ‘full-travel positive tactile feel’ is achieved with the springless magnetic return switch on which normally closed contacts are made via a flexible Mylar printed-circuit board at the base of the keypad.

The range, including full alphanumeric keyboards, will be produced at PED’s Swaffham works in Norfolk, and is expected to generate £10 000 worth of orders in the first year.

The product described above is possibly Series 84.

PED were also scheduled to attend Compec ’82, for which the following was published in Computer Weekly in November 1982:

Three alternative technologies will be displayed in the range of keyboards presented by Pye Electro-Devices of Newmarket. These are springless monolithic keys, discrete keys and electronic touch keyboards. They are shown together with a range of switches, including panel mounted pushbutton, thumbwheel and level switches, and LEDs for panel mounting and circuit board indication.

Series 84

Series 84 was described in the Compec ’81 catalogue as ‘full travel springless alphanumeric “moving diode”’ keyboards.

Series 90

Series 90 was described in the Compec ’81 catalogue as “electronic capacitive touch keyboards”. Potentially this could be the arrangement supplied for the Monarch 120 console.


Capacitive touch

The per-key circuit per the Monarch 120B Compact Call Collect System Technical Description Part 2, page 106 is as follows:

The indication is that PED only produced touch-contact panels and keyboards with this technology, i.e. they were not full-travel switches: each key station responds purely to the operator’s fingers, with no moving parts. It appears that full-travel switches would have been possible.

Mechanical switches

The “PED” switch found in BBC Micro keyboards is the only Pye keyboard switch type encountered to date. It is covered by British patent 2080029 “Push button switch” filed in July 1980 by Philips Electronic and Associated Industries Limited, with Laurence Harry Finlayson given as the inventor. European patent EP0043618 lists both Philips Electronic and Associated Industries Limited and N.V. Philips’ Gloeilampenfabrleken as applicants, and the inventor Finlayson as c/o Pye Electro-Devices Limited. Philips as the owner of Pye filed the patent, but the switch itself was a PED product. The patent itself depicts an illuminated switch, but appears to cover the entire switch design including the contact system; in fact, the patent does not even depict how the lamp leads are routed through or around the switch. The lamp leads are likely supported by the base plug, which presumably came in different forms depending on whether the switch was illuminated or non-illuminated. (Exchangeable base plugs would avoid unused holes in the switch that could allow fluids into the switch during keyboard manufacturing.)

The Philips patent references both Hi-Tek’s own 1972 patent, for their “High Profile” switches, as well as the ITW patent for the mechanical equivalent to Series 555; these existing patents may indicate why the separator bar has a totally different purpose in PED switches than it does in Hi-Tek and ITW switches.


The switches are surprisingly tall: there is almost as much switch below the mounting plate as there is above it. The overall height of the switch is around 16.7 mm from the PCB to the top of the shell (around 19.7 mm with the plunger included). Height above the mounting plate is around 9.3 mm, with around 6 mm below the plate. The switch is around 15.6 mm square at its widest point. Total travel is difficult to measure, but it is somewhere around 3.2 to 3.5 mm.

The switch is plate mount, but it also features two fixing pins, in opposite corners of the base.

Because the contacts are pressed together by the plunger, the feel is distinctly non-linear, but neither is it tactile. The travel starts out linear, up to where the plunger starts to press the contacts together; from here on, the switch is noticeably stiffer. The patent specifically describes how the switch design generates tactility, but the feel is not what one would normally classify as a tactile feel, and the effect is comparatively weak.

The return spring is around 13.7 mm long with five inner turns, 9.4 mm outer diameter, 8.6 mm inner diameter, and 0.4 mm gauge.

View full-size image View full-size image View full-size image View full-size image


To open the switch, press a flat blade screwdriver against one of the retention tabs and press down hard. The top of the switch will release sharply, so be careful to avoid letting the screwdriver enter the insides of the switch too hard.

View full-size image Screwdriver placement
View full-size image Top partially removed; note the now exposed return spring
View full-size image Switch opened

Base plug

Curiously, the contacts are not securely attached to anything. The contacts are held in place by a base plug, which is secured by four lugs. It’s not clear whether the lugs are melted or whether they are intentionally a press fit, but unlike most examples, the base plug can be prised out with a knife and reinserted without damaging the lugs. During initial inspection, the base plug was removed first, before it became apparent how to correctly open the switch. The contacts rest on the base plug, and protrusions from the base of the switch sandwich them between the base and the base plug; as such, the legs are free to move a small amount, and do so when the contacts are closed.

View full-size image Base plug partially removed
View full-size image Base plug removed
View full-size image Contact assembly
View full-size image Symmetrical contacts

Contact operation

Hi-Tek’s much older design used sprung phosphor bronze contacts held apart by a separator bar in the plunger. Pressing the plunger lowered this bar and allowed the contacts to close together. Releasing the plunger would separate the contacts again. The tip of one contact was split into four “fingers” to improve reliability. Later switch designs such as those from Stackpole and SMK would also feature a contact leaf tip divided into fingers.

PED switches also have a pair of opposing contacts, but the design and operation is quite different.

View full-size image Side view of the contacts
View full-size image Top view of the contacts

PED switch contacts are identical, simplifying manufacturing. Instead of having flat contacts with fingers, the contacts bear gold-plated prisms. To allow for the contacts to meet at 90° to each other, the prism is placed at 45°, giving a total angle of 90° between them without needing two different parts.

View full-size image Identical phosphor bronze contacts with prisms

A separator bar exists in the PED design, but for a different purpose. According to the patent, it is to stop the contacts from touching due to external impact. The plungers are instead closed under pressure from a recess within the plunger: the plunger bears an asymmetric guide funnel that drives one contact sideways into the other. This gives the switch its decidedly non-linear feel.

View full-size image Inverted plunger, showing funnel
View full-size image Plunger engaging with contacts
View full-size image Demonstration of plunger–contact engagement
View full-size image Second plunger added for illustrative purposes

During examination, it became apparent that the contacts are forced sideways by the plunger. The patent indicates that the reason for this is to induce a wiping motion, so that the contacts keep themselves clean. Wiping action, incidentally, was also a feature cited by GRI of their KBM switches.


By way of simplistic reckoning, there are seven distinct components in total (parts that can be manually separated), but there are at least nine parts when you consider the prisms.

View full-size image Top views of components
View full-size image Bottom views of components