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 Telestore).

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 allocates resources.
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.

With everything built into the one unit, these proved popular with some call centres, although the additional hardware and even software is now quite rare.