The ICL One Per Desk Computer (known as the OPD)
was released in late 1984 / early 1985 and was based on the Sinclair QL Home Computer, and
included improved ZX Microdrive units and a built in telephone and
modem, phone directory, speech synthesizer and Psion Xchange on
EPROM. It was also released under the name Merlin Tonto for BT
and the Computerphone for Telecom Australia (APT). There were
even a few machines released for North America.
The links between the OPD and the Sinclair QL relate mainly to
the hardware, with the same 68008 CPU, the two main QL ULAs (the ZX8301
and ZX8302) and the built-in microdrives - the same method of RAM and
screen management was also implemented, although most QL software will
not run on the machine. As with the QL, the One Per Desk included
128K of memory (with 32K being used for the screen), but also included
an extra 2K of battery backed CMOS RAM. It appears that the
maximum memory that could be added was a further 128K (giving total
256K RAM), compared to the Sinclair QL - however, as it was planned for
the majority of software to be provided on ROM (for immediate loading),
this is not too much of a problem.
A ROMPACK was released for the computer, which could have
either 2 slots or 4 slots and this was used to good effect to provide
Psion Xchange 2.5 in either a 1MB PROM (the XFAA01) or 256K PROM (the
XBAJ02). Another option which came out of this was the release of
the ICL 128K Memory Expansion Unit (MEU) which included Psion
Xchange 2.5 and firmware for a slow RS232 port included on the MEU.
Another 128K memory expansion was provided by PCML (the
More technical details on the ICL One Per Desk hardware appear
in an article by Murray Macabe.
The Operating System was different to the QL's QDOS, although
it did allow multitasking, part of it was based in the ROMPACK.
Standard software was provided built in, as follows:
KERNEL - manages the hardware, the memory map, input output
device control, and also handles interrupts.
DIRECTOR - is higher level firmware handling applications and the
telephone. It controls START, RESUME and REVIEW key functions and
TELEPHONE HANDLER - manages the 'nuts and bolts' of telephone usage.
TELEPHONE DIRECTORIES - 2 directories are managed, one for telephone
voice calls and one for computer services. It can handle over 500
entries, but this has to be balanced with memory requirements.
CALCULATOR - A simple 16 digit calculator with memory (the CALCULATOR
firmware is in the ROMPACK).
SCREEN IMAGE PRINTER - A screen dump to printer on a single keystroke.
FIELD EDITOR - provides cursor and text editor control.
The following hardware was developed for the ICL One Per Desk
ASYNCHRONOUS COMMS. UNIT (ACU)
The ACU was designed, by ICL, as part of the MEU expansion system and
speeds of up to 19200 bps by, optionally, by-passing the OPD's integral
so allowing high speed communication and networking under control of
one of the
terminal emulation programs. Canadian Standards and ULA approvals were
and the unit was still available from ICL, in early 1988.
This unit's program is called a LOCAL COMMS. CONFIGUPATOR and
of port parameters and operation by ACU or by modem. The ACU was
compliment the MEU, was contained in a steel case approximately 4.5"x
10.5"x1.5" and powered from the OPD, either direct from a ROMPACK slot
alternatively, it could sit on the MEU fed from that unit's 60 way
port. The ACU 'footprint' is the same as the TELEDPIVE's.
The ACU has a single 25 way D connector, RS232C port based on
Intel P80C31BH processor with a 7.37280 Mhz crystal. A series of
multiplexers allow control to be taken over from the OPD, by the
Firmware is provided in 2 EPROMs (a 27C256 and a 27C64). A small ASTEC
encapsulated SMPS is 5 powered from the +5 voLt rails to generate
RS232C port voltages which are not available via the ROMPACK slot (i.e.
-12 volts). Two 2K CMOS RAM ICs provide buffering for data.
Transmission and reception speeds can be specified separately in the
50 to 19200 bps. Other adjustable parameters are word length, parity,
output buffer sizes buffer filling and emptying levels, X-ON and X-OFF
Profiles/patterns for various port configurations can be
set-up, stored in the
OPD PERMANENT STORE and recalled for particular applications.
ASYNCHRONOUS NETWORK COMMUNICATIONS ADAPTOR (ANCA)
This was a free standing, self-powered unit that works with VT-LINK to
provide OPD to IBM
mainframe communications. Full screen working to the IBM host is
speeds up to 9600 bps together with access to the host's applications.
features are included with auto-answer from the OPD.
DATA COMMUNICATIONS ADAPTOR (DCU) - BT Reference 1887
This was provided for the Tonto by BT. It connects via a ROMPACK
is powered from the OPD and provides outputs (via a 25 way, female D
which are compatible with RS232C, RS423 and CCITT V24 standards.
the following terminal types is possible: DEC VT52 and VT100 (80 column
only) and IBM 3278 via a suitable protocol converter. Baud rates from
50 to 9600
can be configured from software. 2400 is the recommended rate.
This provided simultaneous voice and data communications on a single
DESK TERMINAL CONNECTION UNIT (DTCU)
This was a free standing, self-powered, adaptor for connecting OPDs,
running ICL-LINK, to
ICL SME or TME mainframe computers at speeds up to 9600 bps. Full XEM
terminal emulation is provided with dual screen capability and
the OPD. The DTCU microcode (E13100/01) is teleloaded from the
DISTBIBUTED ASYNCHRONOUS TERMINAL SERVICES (DATS)
This allowed you to connect the OPD to ICL DRS series computer systems
via DRS model 110.
ICL Memory Expansion Unit (the MEU)
This was a 128K expansion unit and was intended to be the main unit of
an ICL expansion
system. It had a slow RS232 port (for bar code reading, printers etc.),
capsule slots, a RESET button and a 60 pin expansion port. The MEU was
approximately 10.5"x 7.2"x 1.5". The case was steel with a plastic
overcover and it connected to the One Per Desk via a 6 inch length of
ribbon cable and a modified
ROMPACK case containing line drivers and receivers.
The MEU memory duplicates the basic arrangement in the OPD and
is controlled by
a ZX8301 with a 12Mhz crystal. The address lines to the ULA are
position the memory at the expansion addresses. Two 74HCT2S7s provide
address multiplexing and a 74HCT245 acts as the data bus transceiver.
itself uses four 256K DPAM ICs (81464 devices, each 64Kx4 bit).
XCHANGE version 2.5 is included in the unit, provided in two
PROMs. A third ROM, a 27C64-25 EPROM,
carries firmware to initialise the new memory and service the RS232
As this was bulky and expensive, it was soon superseded by the
PCML TELESTORE unit.
This allowed files to be transferred between OPDs and IBM PCs.
The Mega Capsule is an extended Capsule housed in the case supplied for
cable connection from the Rompack to the Teledrive or ACU. Inside, an
enlarged PCB carrying 2 x 27512 EPROMs, a small capacitor and an HCT04.
The Capsule utilises memory paging techniques to handle the extra EPROM
The Ramcap is of much later design and consists of a bank of four
HM66202L-15 surface mounted Ram chips backed by a 3v Lithium battery.
On one side is a small slide switch labelled Write protect -
Write enabled. This unit was employed for the development and testing
of software. It is possible to load software into the unit, reset the
OPD and test. The unit also makes software (not yet in EPROM) to be
ported to different versions of the OPD for compatibility testing.
This allowed the OPD to be used as a Telex station
This was a security device produced by PCML. It consists of an in-line
assembly which plugs into the 2 'D' connectors on the OPD control unit
supplies/video and the printer connectors) and provides 2 new 'D'
its outboard end, for the original leads. There is a lock on the unit
by a Yale type key. The OPD can be disabled, for security purposes by
and removing the key.
TELESTORE Memory Expansion
The PCML 128K memory expansion, TELESTOPE, fits into a ROMPACK case.
original version had 4 'slots' plus version 2.5 of XCHANGE. A later,
1987 version, was built into an extended case and accommodated 6
PCML designed the TELESTORE with a fairly standard ROMPACK
base board plus a
'piggy-back' board containing the extra memory. Unlike the standard
main components are soldered into the board to cut down height and
assembly to fit into the standard case. The 'piggy-back' memory board
on a 34 way, in-line header strip.
The 128K memory is 4 off 4464 ICs (64K x 4 bit each),
controlled by a Toshiba
TC17G014AP-12 CMOS gate array which is custom programmed and uses a 12
crystal. The 'piggy-back' board also contains two 74HCT257 address
and a DIL resistor network.
The base board contains 2 PLA devices, buffers and XCHANGE 2.5
in two ROMs. The
ROMs are the ICL/PSION XFAA01 and a 27C512 EPROM containing the
XCHANGE plus the initialisation firmware for the extra memory.
Both the MEU and TELESTORE included special initialisation and
for the memory expansion. When an OPD is powered-up with TELESTORE (or
connected) the screen displays that an 'Invalid Capsule' is present and
HOUSEKEEPING shows the standard free store capacity of about 150
special initialisation routine then checks and logs-on the new memory
updated HOUSEKEEPING Store Report shows the increased memory of about
blocks. This extra process takes about 15 seconds and does not cause
illumination of the line LEDs, as in the normal initialisation.
We have started a project to resurrect a disk drive for the
ICL One Per Desk and derivatives - see our page on ICL One Per Desk Storage Solutions.
The following software was released for the One Per Desk
A program for creating special spreadsheet templates for income tax,
financial reports etc. by Patrick and Leach.
Satellite Computing produced an ACTION DIARY.
ACTION DIARY 2
An upgraded version of ACTION DIARY from Satellite Computing
ADVANCED MESSAGING (BT Reference M1822)
An expansion of MESSAGING which occupies 2 capsule slots, providing all
the facilities of Messaging plus auto-retry; multiple addressing and an
interface facility with EXPORT format files.
A program to simplify basic ARCHIVE application which the user can then
to his individual needs. It requires XCHANGE vers. 2.5. and was
Ark Distribution. This program was also released for the Sinclair
BASIC COMPILER and INTERPRETER
This also was from Computer One and intended for release as a special
ROMPACK assembly. XCHANGE was not available with this ROMPACK but the
system included an editor for program preparation. The Compiler and
Interpreter were Microsoft compatible and provided performance
improvements of 3 to 4 over OPD Basic.
BASIC TELEPHONY INTERFACE
A Satellite Computing Romcap linking Basic programs and the telephone.
A program from Control-C Software for jotting down ideas which can be
a later date.
C COMPILER and ASSEMBLER
A 3 capsule set from Computer One was scheduled for release
in mid-1986. The Compiler was in 2 capsules and the Assembler in one.
These were to be supplied with a 4-slot ROMPACK containing XCHANGE with
QUILL being used to prepare and edit programs.
This was available from PSION for the OPD with 28 levels of play.
Combines the functions of ICL-LINK, VT-LINK and TERMILINK in a single
capsule. This is incompatible with VT-LINK 2. If both are fitted to the
ROMPACK at the same time the OS will log-on only the VT-LINK * program
with the lowest memory address.
Metacomco supplied a cross-development package which allows OPD
software to be
developed on an ICL or IBM PC.
DATALINK (BT Reference M1824)
A single capsule introduced to overcome, in part, the isolation of the
XCHANGE programs from the communications facilities. It allows incoming
communications data (from a computer service or mainframe) to be
imported to XCHANGE. It also allows QUILL format files to be exported
by the communications facilities of the OPD.
A Capsule from MGB Micro Products which allows the OPD to auto-log-on
and auto-answer when used in conjunction with the MGB Dialback Security
ICL - DEMO (BT Reference M1853)
A demonstration program for XCHANGE including a '.dbf' file on
geography for working through ARCHIVE.
Occupies l capsule slot, allowing communication with ICL mainframe
computers and emulation of a full XBM Screen Mode Terminal. ICL-LINK
requires a Desk Terminal Connection Unit (DTCU) for the link interface.
ICL OPDBASIC (BT MERBASIC Reference M1851)
BASIC is not resident in the OPD. It is loaded from microdrive and is a
subset of Sinclair QL SuperBASIC. It lacks SuperBASIC features
especially graphics such as LINE, CIRCLE and ARC. In multi-tasking,
there is insufficient memory to store several complete graphics screens
and recall them with the RESUME and REVIEW keys.
ICLBASIC was intended as a high level bridge to QL software
but, as such, it has limited capabilities. BASIC version 07 was
available in 1986. The version in use can be displayed by the PRINT
VER$ command. The early Basic versions included features which were
discontinued in later versions e.g. Ver. 5.02 includes Tokenised SAVE
and PUBLISH commands TK_SAVE and TK_PUBLISH respectively. These allow Basic
programs to be saved in a coded form with a table of keywords and
commands. This increases the length of small and medium files but can
reduce programme loading times by factors up to 3 (and are similar to
the QL's QLOAD software).
The BASIC cartridge contains the factory-set default values of
the PERMANENT STORE plus configuration programs for the OPD, the
printer and the telephone (CONFIG, CONPRIN and CONTEL respectively).
ICL/PSION - HELP (BT Reference M1854)
HELP files for the XCHANGE programs are provided as a microdrive
ICL WELCOME (BT Reference M1850)
This cartridge was supplied as part of the WELCOME package to provide
information and to demonstrate the equipment's capabilities to the new
ILLUSTRATOR EGO (Executive Graphics Option)
Occupies 1 capsule slot, allowing connection of an QPD to an ICL
mainframe (via ICL-LINK, and a DTCU ) to view professional graphics on
the OPD. Graphics may be viewed and stored on microdrive but cannot be
altered or edited by the OPD.
INTERFILE (BT Reference M1823)
Occupies 1 capsule slot allowing file transfer from OPD-to-OPD via the
modem. Facilities include auto-retry and transmission at pre-set times.
The INTERFILE ROM includes 'patch' code to permit more than 6 ROM
applications to be connected to the OPD at the same time.
Another implementation of Basic for the One Per Desk produced
by MetaComCo for American versions of the computer. Originally in a
Mega Capsule, it was later available for installation in a standard
2 slot ROMPACK. This version of BASIC was more compatible with early
Basics such as GWBasic and MBasic starting with the familiar 'Ok'
screen prompt - however, enhancements were made to make it compatible
with both ICL Basic and Microsoft Quick Basic.
This Basic forms part of the system for use with the Basic Compiler for
Programs are written and tested in Basic then compiled.
Some documentation available.
Better BASIC Quillinan, (Butterworth, 1985)
The MBASIC handbook Ettlin & Solberg, (Osbourne/McGraw Hill 1983)
MC BASIC Reference Manual , (Metacomco plc 1985)
MC BASIC COMPILER
Originally consisted of a Mega Capsule only
intended for use with the later version of the OPD bound for the USA.
The Mega Capsule employs memory paging techniques that are incompatible
with a standard OPD. However, the program has been copied to 4 x 32k
EPROMs and can be inserted into a standard 2 slot ROMPACK.
The package was written by Computer One and consisted of:
MC Basic Compiler
The menu also lists a linker, but it has been confirmed that this
section was never completed.
The compiler output carries a large overhead of library sub-routines
making small applications uneconomic in terms of memory. Once past the
'threshold', however, larger programs are most suitable. Should a suite
of programs be running together, it is necessary only to load the
library once. An option exists at compiler run time to exclude the
Alas, no documentation is available which covers the OPD
version of the Assembler or Compiler.
Although officially required to compile MC Basic, many of the features
of ICL Basic for the OPD (itself a variant on the Sinclair QL's
SuperBASIC), are included in tandem. This gives access to the superior
features such as user defined Procedures instead of position dependant GOTO and GOSUB.
compiler also has the ability to compile Basic lines that MC Basic
rejects, for example the command line(x,y)-(a,b)
is rejected by MC
Basic but can be compiled and actually allows the user to draw a line
on screen, despite the fact that ICL BASIC does not contain any
The compiler writes a run-time library for each program that
takes up about 20k. Small programs will therefore occupy relatively
more space. Medium to large programs will save space due to the
re-using of library routines. The main advantages of the compilation of
the program is in speed of execution, memory usage (there is no need to
load Basic), and the ability to choose the program from the
Some documentation is available but no 'official' handbook was written.
MESSAGING (BT Reference M1821)
A single capsule which provides desk-to-desk text messaging between
OPDs; unattended receipt; auto-send; dump to microdrives and a print or
A capsule from MGB Micro Products including all the facilities of
DB-LINK plus the ICL-LINK terminal emulation package.
A business forecasting program from Control-C Software.
PLANT DATABASE SYSTEM
Superplant Software offered a database system which uses ARCHIVE to
help with tree
and plant selection and care.
A cut down version of WordStar for use with the TELEDRIVE disk unit
A Satellite Computing Romcap providing a graphics display system for
producing transparencies and designing, and running, flipchart style
presentations using a rolling, on-screen display.
This was produced by Satellite Computing.
QL/OPD INTERCHANGE PROGRAMS
These were written by Dave Walker
and consist of a QL/OPD FILE INTERCHANGE program and a QL/OPD DIRECT
TOOLKIT. The same author produces the MultiDISCOVER program which
allows disks to
be interchanged between the QL and PC compatibles and can even be used
to allow the QL to write to disks that the TELEDRIVE can read.
A computer access page store with enhanced facilities including
archiving, organising and merging of stored pages and self-running
Provides terminal emulation for the ICL 6402 and 6404 QUATRO
series desktop computers.
A small business accounting package from A.M. Programmers.
Produced by Computer One.
VT-LINK/VT-LINK 2 (BT References M1825/M1826)
Occupies 1 slot and provides terminal emulation for communication with
Digital Equipment Corporation (DEC) VT series computers. VT-LINK covers
VT52 and VT100 emulations. VT-LINK 2 covers the VT52, and VT102. Its
manual states it also covers VT100. VT-LINK 2 includes an
improved printer configuration program CONPRIN allowing condensed 132
column printing in some applications. This CONPRIN can conflict with
the disk based CONFIGURATION programs supplied for TELEDRIVE.
This was a standard suite of business programs released by PSION in
various guises. It was available for the Sinclair QL as four separate programs
originally (Quill - word processor: Archive - database: Easel business
graphics and Abacus - spread sheet), and as an integrated suite for the
ICL One Per Desk as XChange and as PC Four for DOS based
computers. The integrated package included several enhancements
over the original individual programs, including the TSL Programming
Language which allowed you to create a program to control
XChange. Xchange has since been made available for the Sinclair
QL, with the permission of Psion.
On the One Per Desk, XChange is provided in ROM, as an option,
and mounts in the ROMPACK. Version 2.5 was in service by mid 1985 but
units are generally the earlier version 2.3 (the version number is
displayed when entering XCHANGE from the
In general the 2-slot ROMPACK
has version 2.3 and the 4-slot ROMPACK, TELESTORE and the MEU have
Century Communications Ltd. (Newtech Publishing Ltd.) produce 3 guides
to the 'Merlin-Tonto' at a listed price of £12.95 each. These books are
user orientated and contain no significant technical detail of the
internals of the 'Tonto'.
"Business Communications with the Merlin Tonto" by Martin Gandoff ISBN
"Introducing the Merlin Tonto" by Garry Marshall ISBN 0-09-161661-1
"Business Computing on the Merlin Tonto" by Stephen Morris ISBN
The following user manuals were provided by ICL or BT:
14 INCH COLOUR MONITOR (BT Reference TPU 17J)
Advanced Operations (BT Reference TPU 12G)
Basic (BT Reference TPU 12C)
EGO Illustrator (Leaflet only)
Exchange quick reference (BT Reference TPU 192)
Handbook (BT Reference TPU 12B)
Installation (BT Reference TPU 12A)
Installing Telephone Lines and Sockets (BT Reference TPU
Interfile (BT Reference TPU 428)
M1880 Printer Manual (BT Reference TPU 249)
M1881J2 Printer Manual (BT Reference TPU 332)
MERLIN TONTO Some Questions and Answers (BT STAFF ONLY)
Messaging (BT Reference TPU 12D)
MP1887 Datacomms Adaptor (BT Reference TPU 116)
OPD VT100 LINK (BT Reference TPU 334)
OPD Programmers Manual (ICL - approx 700 pages, complete
with development ROM)
OPD Serivce Manual (ICL - Details unknown)
Using MP11881 With Tonto (BT Reference TPU 439)
VT-LINK 2 (BT Reference TPU 730)
Welcome Package (BT Reference TPU 12F)
Xchange (BT Reference TPU 12E)
XCHANGE Quick Ref. Card (BT Reference TPU 242)
ICL also issued a supplement giving guidance on interfacing
various printers to the
OPD. It detailed the parameters to be set by CONPRIN and which features
standard OPD/OKI package are not available with other, identified
A supplement was issued on MESSAGING giving greater detail of
and expansion of information on turning the T-LINK protocol on and off.
We would welcome copies of any of these manuals or the ability
to make them available once again.
One of the main problems which One Per Desk users face is
finding a compatible printer. The One Per Desk uses a 9 pin RS423
port which is RS232 compatible for use with a printer - it is one way
only. Unfortunately, modern printers are unlikely to be
compatible. As more and more printer manufacturers strive to
reduce costs by removing components, they presume that computer users
have a Windows or MAC based operating system which will translate all
text into the graphics code for them. As a result many printers
no longer support a parallel or serial port (which is required by the
OPD) and do not allow text to be sent to the printer direct.
If you want to use a standard centronics (parallel) printer
with the One Per Desk, you will need a serial to parallel
converter. Alas we have not managed to get any of the standard
ones to work and would have to rewire
Sinclair QL converter.
About the best supported printers are those manufactured by HP
and Epson, although you have to be extremely careful about which model
you have - a full Epson ESC/P2 or HP PCL-4 control set are required for
the One Per Desk to fully support the printer. About the best
inkjet which can be obtained fairly reasonably and is fully compatible
with the OPD for text, has to be the Epson 850 or Epson 900
We can sometimes provide compatible printers and serial to
parallel converters second hand.