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ICL One Per Desk

(adapted from articles appearing in Micromart and Sinclair QL World)


The One Per Desk was the eventual fruit of a long-running but troubled collaboration between Sinclair and ICL, initiated in 1981.  The machine was intended for the busy executive with only limited computer skills. Most operations use multiple choice menus.  The original machine was, like the QL itself, intended to incorporate a revolutionary new flat screen display being developed by Sinclair.  However, the technical problems of developing a flat-screen display tube prevented it from being used with either machine (the tube was eventually used for the TV80 pocket television).  The QL's well-publicised difficulties added further delays.

The OPD was finally released in early 1985.  BT's Merlin division subsequently marketed a repackaged version under the name of "Tonto" - rather unfortunately, this means "silly" in Spanish. Another rebadged version was produced for Australian Telecom as the Computerphone. Many hundreds were sold to local authorities, government departments and large companies in both countries, but the OPD seems to be very rare nowadays - I understand that not even its makers, ICL, have one in their archive.



Despite the radically different exterior, the hardware is based primarily on the QL.  The OPD CPU is a 7.5 MHz 68008, which has a 16/32 bit internal architecture, but only an 8-bit external data bus. It is assisted by two Uncommitted Logic Array (ULA) custom chips, marked ZX83 - the Sinclair Research house-name for the QL (ZX82 being the Spectrum, following the pattern set by the ZX81 and ZX80). As a result, the real time clock, screen management and dynamic RAM control method, all copy those of the QL. Of the 128K DRAM, 32K is allocated to the screen, leaving only around 75K as workspace, after other standard demands have been catered for. An additional 2K of battery-backed CMOS static RAM holds a permanent store for system configuration Formation.

The DRAM workspace is treated rather like a RAM-disc by the OPD operating system. It is referred to as STORE, and is intended to remain continually active, since the machine is designed to be left permanently under power.

This philosophy of instant availability extends to other aspects of the hardware and software. In particular the software is principally ROM based. 128K of operating system is carried in 4 ROMs mounted on the internal CPU board. This narrow PCB (19 x 4.5 cm) looks very much like an afterthought. It houses the socketed MC68008P8 CPU, with all 48 pins passed directly through to a DIL connector on the OPD / Tonto main PCB. A further 28pin DIL connector to the main circuit board, sits over what appears to have been planned as a 32K ROM socket.

The piggy-back CPU board also carries the Texas Instruments TMP5220C speech synthesiser IC, which has 16K of custom ROM under direct control.

ROM applications software comes in two forms, connected via the ROM-pack bay. The ROM-pack itself holds up to 160K, but can also take plug-in capsules around the size of a matchbox, with 8, 16 or 32K capacity each.  The minimal ROM-Pack has a single 32K PROM loaded with odd operating system software together with an emulator for a desk calculator. As an optional extra, ROM-packs were available with five 32K PROMs holding 144K of the QL's Psion software suite, in addition to the calculator.

Early OPD machines came with ROMpacks having only two 30-Pin slots for capsules. By replacing four of the 32K PROMS with a 1 Mbit chip (available in mid 1985), ICL were able to make room for two further capsule slots in the 4-slot ROM-pack. Memory addresses for these slots differ from those in the 2-slot ROM-pack. Thus, the OPD has the potential to handle six capsules in total, with up to 192K of ROM. Probably the majority of OPD machines were supplied with a 2-slot Xchange ROMpack. On fitting a couple of large-capacity capsules, you have a respectable 350K of ROM software at hand, ready to operate on your data files held permanently in RAM store.

Later improvements included disk drives from PCML (with 256K extra memory), and another from Computer One, but these are no longer manufactured and can only be obtained on the second hand market. A variety of plug-in capsules were also provided, but most were to enable the OPD to link to ICL mainframe computers and are of little use to enthusiasts. There were later options to allow direct transfer of files direct from microdrive, via the telephone line, between OPDs and to import data into Quill or Abacus from bulletin boards.

It is not possible to simply plug-in extra memory as on the QL because the OPD requires special code to 'log-on and identify' the memory. A 128K expansion unit was made but few seem to have been sold.


The machine has a 'footprint' of about the same length but twice the depth of the QL. The sloping console carries a telephone handset to the left of the keyboard. A combined dialling/numeric keypad is at the keyboard's right. Above, a projecting ridge houses two microdrives.  At the rear of the keyboard unit (above), two expansion bays provide a plug-in socket for a ROM-pack and space for a large modem, which connects externally to the handset and to two telephone lines. 


The modem was designed as a plug-in to enable easy adaptation of the OPD for use in different countries or for future development, and additional versions were produced in small quantities for Australia, North America and south Africa. The British version was designed by British Telecom.

Modem facilities are handled by a 7910 chip, giving V21 and V23 modes of 600 or 1200 bps half duplex and 300/300 or 75/ 1200 bps full duplex. The transmission protocol (parity and stop, start and data bits) is configurable from internal software. Pulse or tone dialling can be selected by DIL switches on the circuit board.

The modem is built-in and capable of Viewdata and Glass Teletype communications. This enables connection to Prestel, Yellow Pages, Tony Firshman's Board and many others. Screens can be saved to memory using the 'Snapshot' option, or entire programs can be downloaded to microdrive. Text can be prepared off-line to save phone charges.

The numeric keypad to the left of the main keyboard is arranged like that of a telephone, and is used for manual dialling. It also carries 12 command legends for activating telephone-related operations. For example: LAST displays the last six numbers dialled and redials your choice; HOLD holds a call; SPKR initiates or transfers a call to the loudspeaker; SELECT switches to the other line.

The LIST key gives a single-screen directory listing of priority telephone numbers. These are a selected subset of the main telephone directory, which can hold over 500 entries for automatic or 3-letter shortcode dialling.

Names, addresses and descriptions in the directory can be located by a key-word search facility, or simply by browsing. Directory entries can specify a chargeband code to enable the costing of calls. This can also be initiated using the TIMING key on the dialling pad.

A separate computer access directory duplicates the facilities of the telephone directory, but also stores information on the profiles of connection protocols for establishing each data link.

Auto-answer data mode permits the reception and storage of data without any user intervention.

In voice auto-answer mode, the speech synthesiser can select from 16 pre-assembled messages for replying to incoming calls. This can be set to reply to incoming voice calls by speaking a message selected from 16 pre-assembled responses. These are composed from two screens containing 152 words, the individual letters A-Z and the numbers 0 to 59 together with 1st to 31st. Long or short pauses and -s or -ing suffixes are also allowed.

The minimal Basic English vocabulary of the speech synthesiser consists of 850 words. However, the OPD vocabulary is specifically selected for telephone responses, and so is quite adequate for the intended polite business-like messages, though the machine finds it hard to cope with anything beyond this.


Two colour display models are found with OPDs. Both are by Microvitec, and are similar to the CUB, sold extensively for the QL. The earlier version is medium resolution, but was superseded by a high resolution 1441 model, distinguished by its central OPD badge below the screen.

A single D15D15 cable connects the console to the monitor, bringing in power lines from the PSU and carrying back RGB TTL colour signals. The 15 pins of the D connector to the monitor are as follows:

- to the display:

D10=on indicator;

- from the PSU:


On the 9" mono display, the RGB signals are combined on a small ICL PCB, before being passed to a Philips VDU chassis. This allows colours to be reproduced as grey shades.

The OPD is designed to be left on and the screen will blank if no keys are pressed for 10 minutes. Pressing any key, or an incoming call, re-activates the screen. For longer periods of inactivity, frontal switches on both the mono and colour monitors can be used to shut down power to the display, without affecting the OPD itself.

Like the QL, the maximum display resolution on the OPD is 256x512, with only black, white, green and red available. This is equivalent to 26 lines of 80 normal or 40 double-width characters, though the bottom two lines are reserved as a status display area for the system and telephone indicators. By halving the horizontal resolution the number of colours can be increased to eight.


The One Per Desk's greatest weakness is its reliance on Sinclair's microdrive technology.  The two built-in microdrives are similar to those on the QL, but save the data in a different density. Blank cartridges can be used on either machine, but the OPD cannot read QL cartridge data, although there is a program (for the QL) that can convert data and Basic from the OPD to the QL and vice-versa. The OPD records cartridge use and read failures, and warns when the cartridge is due for renewal. Thanks to improvement work by ICL, the microdrives are considerably more reliable than the Sinclair originals.  However, they are still tediously slow: it takes around 45 secs for formatting, about 2 mins to save a 1K file and a yawn-inducing 10 mins or more to copy a full cartridge file by file.

Printing and networking

The OPD is provided with a serial port, but one which works in one direction only, being intended solely for printer use.  The serial port uses a 9-pin D connector with data on pin 1, ground on pin 2, and status on pin 3. Rebadged Okimate 20 thermal printers were commonly supplied for the OPD by ICL. These are neat little units of about A6 size. They have a draft mode at 80 cps and a half-speed NLQ mode. Printing can be on thermal paper or on ordinary sheets using a thermal transfer ribbon. Colour ribbons can also be loaded and are supported by the OPD software.

The OPD's serial port can also be used to download Basic files directly to the QL, using the SER2 port on the QL and a suitable cable. No input from the QL is possible by this route.


The software is an enhanced suite of the Psion programs supplied with the QL (Abacus, Archive, Quill and Easel) with the import/export of data between applications simplified. Being ROM-based, it loads quickly and without read failures. The four are brought together under an operating 'shell' called Xchange Task Control. Up to eight 'tasks' can be in progress at one time. Import and Export between Psion programs is fast and simple. Xchange was an optional extra.

Basic is loaded from cartridge and is a reduced version of Superbasic. Many of the features of Superbasic are not available on the OPD. There are no graphics as such (CIRCLE, LINE, BORDER, FLASH etc.), no EXEC and no DIR. The screen size is also slightly smaller. QL Superbasic programs can be transferred to the OPD but need considerable editing before use. Although using the same CPU, QL machine code programs cannot be run on the OPD. There are differences in the way the OPD handles the screen etc. that make QL programs incompatible.

Communications software is built in for emulating an intelligent terminal. This can be either a Viewdata type of terminal (75/1200bps) or a 300/300(V21) to 75/1200(V23) bps "Glass Teletyped". The latter sounds rather antiquated, but essentially it provides most of the basic requirements for terminal access via the modem.

With it you can select the protocol for the communication link (linespeed, parity, stopbits, echo, etc) and set up character strings for sending with a single key press. Incoming data can be continuously monitored, or acquired in screen snapshots, by the printer or OPD RAM page store. This holds up to 99 pages, for subsequent examination or printing at leisure.

Sadly, the reverse action of sending prewritten pages of text down the data link is not provided for. To achieve this you require a specific version of the many types of comms software on ROM capsule.

The range of such capsules allows emulation of a wide variety of old terminal types. VT-LINK emulates DEC VT52 and VT100 terminals; VT-LINK2 does the same for VT102; ICL-LINK emulates DRS20 and 7561; TERMILINK does 6402 and 6404 ICL standards; DGLINK handles Data General.

For this you need the capsule DATALINK, which allows text files to be transferred to and from Xchange applications, such as the Quill WP, via the microdrives. DATALINK was introduced rather late on, to meet, in a primitive way, the fairly obvious requirements of integration between two aspects of OPD software. Compartmentalisation of software units, with little or no provision for inter-communication, is a significant shortcoming of all the OPD utilities and applications.

A good example is that of 'Messaging', a fax look-alike, with which many OPDs were supplied.  The capsule contains a ROM with the necessary code, which enables OPDs to send pre-types text to each other using the telephone system. Received Messages can be edited and sent on to other users, printed or saved on microdrive. Later ROMs allow the messages to be sent at pre-set times and to different numbers to take advantage of cheap rate calls.

Somewhat offsetting these useful features, however, it was not originally designed to interface either with the Xchange WP Quill or the OPD main telephone directory - you have to transfer names, phone numbers and charge bands by re-typing. It is almost as if the writers had never seen any of the other OPD software.   Eventually a 2-slot "Advanced Messaging" capsule did add the capability of handling Xchange files, but this was a late introduction.

Third-party software is in very short supply, although some business oriented programs were produced. A diary/appointments program has been seen and a CP/M operating system is available on one version of the disk drives. It is reported that Basic and C compilers were also produced.

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Chris Owen 1994-2003