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
following the pattern set by the ZX81
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
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
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
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
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
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:
- 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.
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
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
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
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
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
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.
© Chris Owen 1994-2003