NEW
Expansion Systems
This section documents expansion systems for the Sinclair ZX Spectrum,
including backplanes, motherboards, interface cards, daughterboards,
adaptors and packaged systems. Related components should be described
together as product families where appropriate, so that the relationship
between a main system and its optional modules remains clear. Technical
details, original prices and contemporary references are included where
these can be established from surviving sources.
Features
Original Price
BASICare
BASICare Microsystem Ltd
BASICare, produced by BASICare Microsystems Ltd, is a modular expansion system for the Sinclair ZX Spectrum. Known as the “Tower of Power”, it consists of individual modules that connect to the PERSONA SP interface, providing additional memory, storage, sound, timing and input/output facilities. PERSONA SP connects directly to the computer's rear expansion connector and provides a buffered 64-way connection for BASICare modules 1 2.
The Spectrum module range includes RAM08 and RAM16 memory modules, RAM64 for extended memory, and DROM for non-volatile storage of programs and data. DROM provides up to 8K of memory using four sockets for CMOS 2K RAM chips. Individual write-protection switches protect each chip, while an autostart facility can execute routines when the computer is switched on. Supplied software includes utilities for BASIC line numbering, machine-code resetting and accessing the CLOCK module. TOOLKIT supplies utilities in EPROM, while other modules extend the computer's capabilities with a battery-backed real-time clock (CLOCK), a three-voice sound generator (SONUS), 24 lines of input/output (PERICON A), a Centronics printer interface (PERICON C) and an eight-channel analogue-to-digital converter (LINK A) 2.
The modular design allows users to configure the system for specialised applications, including hardware control, data acquisition and machine-code programming. The contemporary review also describes the practical limitations of memory paging when used with conventional Spectrum BASIC programs 2.
The Spectrum module range includes RAM08 and RAM16 memory modules, RAM64 for extended memory, and DROM for non-volatile storage of programs and data. DROM provides up to 8K of memory using four sockets for CMOS 2K RAM chips. Individual write-protection switches protect each chip, while an autostart facility can execute routines when the computer is switched on. Supplied software includes utilities for BASIC line numbering, machine-code resetting and accessing the CLOCK module. TOOLKIT supplies utilities in EPROM, while other modules extend the computer's capabilities with a battery-backed real-time clock (CLOCK), a three-voice sound generator (SONUS), 24 lines of input/output (PERICON A), a Centronics printer interface (PERICON C) and an eight-channel analogue-to-digital converter (LINK A) 2.
The modular design allows users to configure the system for specialised applications, including hardware control, data acquisition and machine-code programming. The contemporary review also describes the practical limitations of memory paging when used with conventional Spectrum BASIC programs 2.
Notes
A contemporary review in Your Spectrum, issue 3, May 1984, confirms that BASICare was tested on the ZX Spectrum. The review discusses PERSONA SP, CLOCK, RAM expansion, DROM, autostart and memory paging. It notes that most module documentation originated with the ZX81 and was accompanied by Spectrum update sheets.
The Sinclair User advertisement separately lists PERSONA ZX81 and PERSONA ZX Spectrum, alongside expansion modules and prices. It also lists MINIMAP and PERICON B, but their compatibility with the ZX Spectrum has not been established.
The Sinclair User advertisement lists DROM (2K) at £39.50, with an additional 2K available for £7.50. The Your Spectrum review describes a DROM module containing four sockets for CMOS 2K RAM chips, providing up to 8K of non-volatile memory. The reviewed unit had 4K fitted. These descriptions may refer to the same module with different memory configurations, although this has not been conclusively established. The Your Spectrum price of £48.00 is used for the Spectrum entry.
The Sinclair User advertisement prints the optional module name as USERFRONT, which appears to be a typographical error for USERFONT. Its compatibility with the ZX Spectrum has not been conclusively established.
The Sinclair User advertisement separately lists PERSONA ZX81 and PERSONA ZX Spectrum, alongside expansion modules and prices. It also lists MINIMAP and PERICON B, but their compatibility with the ZX Spectrum has not been established.
The Sinclair User advertisement lists DROM (2K) at £39.50, with an additional 2K available for £7.50. The Your Spectrum review describes a DROM module containing four sockets for CMOS 2K RAM chips, providing up to 8K of non-volatile memory. The reviewed unit had 4K fitted. These descriptions may refer to the same module with different memory configurations, although this has not been conclusively established. The Your Spectrum price of £48.00 is used for the Spectrum entry.
The Sinclair User advertisement prints the optional module name as USERFRONT, which appears to be a typographical error for USERFONT. Its compatibility with the ZX Spectrum has not been conclusively established.
Gordon Microframe
Gordon Micro Ltd
The Gordon Microframe, produced by Gordon Micro Limited, is an expansion system for the Sinclair ZX Spectrum that plugs directly into the computer's rear expansion connector. It provides a five-slot card frame for adding compatible hardware, with buffered signal lines to help maintain reliable communication between the computer and connected devices. Its decoding circuit supports up to 256 input/output (I/O) channels, allowing the Spectrum to communicate with a wide range of external equipment 3.
The system also includes a floppy-disc controller that can connect up to two mini or micro floppy drives. A built-in PROM starts the disc operating system, loading it into 16K of on-board memory that temporarily takes the place of the Spectrum's BASIC ROM. This allows the system to provide disc-related commands such as LOAD, SAVE, MERGE, ERASE, CAT, OPEN and CLOSE. An external reset button is also provided 3.
The system also includes a floppy-disc controller that can connect up to two mini or micro floppy drives. A built-in PROM starts the disc operating system, loading it into 16K of on-board memory that temporarily takes the place of the Spectrum's BASIC ROM. This allows the system to provide disc-related commands such as LOAD, SAVE, MERGE, ERASE, CAT, OPEN and CLOSE. An external reset button is also provided 3.
Gordon Microframe
Spectrum attached to Gordon Microframe
£149.50
3
Price included VAT; postage and packing were an additional £3.00.
MUKBUS Cardframe System
Microtext (U.K.) Ltd
MUKBUS, produced by Microtext (U.K.) Ltd, is a modular expansion system for the Sinclair ZX Spectrum and ZX81. The MUKBUS card frame provides six expansion slots with a fully buffered 64-way signal bus, an on-board reset switch and a Sinclair edge-connector expansion interface. A dedicated power supply is available to power the expansion bus and disk systems, while an optional keyboard provides a typewriter-style layout with colour-coded keys, a cursor pad, an automatic Delete key and unassigned keys for engineering applications.4
The advertised range also includes additional interface boards announced as forthcoming, covering 32K RAM expansion, disk access, barcode reading, 80-column video, digital-to-analogue conversion, high-resolution colour graphics and Centronics/RS232 connectivity.4
The advertised range also includes additional interface boards announced as forthcoming, covering 32K RAM expansion, disk access, barcode reading, 80-column video, digital-to-analogue conversion, high-resolution colour graphics and Centronics/RS232 connectivity.4
Specspansion
F B tronics
Specspansion, produced by F B Tronics, is a modular expansion system for the Sinclair ZX Spectrum, combining a four-slot motherboard with an integrated 24-line bidirectional programmable port board. It plugs directly into the Spectrum's rear expansion connector and provides an edge connector for attaching the ZX Printer and other peripherals 5 6.
An on-board +5V regulator supplies power, while built-in address decoding at three of the motherboard slots provides for up to twelve additional ports 6.
The system accommodates additional interface cards and can be supplied drilled only or with additional connectors fitted, allowing users to expand the hardware in stages. A comprehensive user manual is supplied, with an optional programming-aid cassette available separately 5.
An on-board +5V regulator supplies power, while built-in address decoding at three of the motherboard slots provides for up to twelve additional ports 6.
The system accommodates additional interface cards and can be supplied drilled only or with additional connectors fitted, allowing users to expand the hardware in stages. A comprehensive user manual is supplied, with an optional programming-aid cassette available separately 5.
USP ZX Spectrum Expansion System
U-Microcomputers Ltd
The USP Spectrum Expansion System, produced by U-Microelectronics Ltd, was a modular hardware system designed to extend the Sinclair ZX Spectrum's input/output, communications and printer capabilities. The system used a back-to-back adaptor and buffered backplanes, allowing interface cards to be installed and additional slots added as required.7
The system comprised the following modules:
USP-ADAP — Back-to-back adaptor: Connects the Spectrum to the USP expansion system.7
USP-BBP3 — Three-slot buffered backplane: Provides three expansion slots and a side connector for compatible peripherals. Requires an auxiliary power supply.7
USP-BPE4 — Four-slot backplane extension: Adds a further four expansion slots when connected to the USP-BBP3.7
USP-PROT — Prototyping board: Provides a board for developing and testing custom interface circuits.7
USP-232D — Dual-channel RS232 serial interface: Uses a Z80DART chip and supports baud rates from 75 to 9600, with full handshaking. Supplied with a terminal emulator and a 50-page manual.7
USP-I/O — General-purpose parallel interface: Uses a Z80PIO chip to provide two eight-bit input or output ports with four handshake lines. Supplied with a 30-page manual.7
USP-CENT — Centronics printer interface kit: Adds Centronics-compatible printer connectivity to the USP-I/O, including a cable and software drivers for LPRINT and LLIST.7
USP-PRINT — Packaged printer interface: Based on the USP-I/O board and supplied assembled and tested, with a Spectrum adaptor, cable, comprehensive manual and cassette software.7
The modular design allowed users to combine interface cards according to their requirements and expand the system as additional hardware facilities were needed.7
The system comprised the following modules:
USP-ADAP — Back-to-back adaptor: Connects the Spectrum to the USP expansion system.7
USP-BBP3 — Three-slot buffered backplane: Provides three expansion slots and a side connector for compatible peripherals. Requires an auxiliary power supply.7
USP-BPE4 — Four-slot backplane extension: Adds a further four expansion slots when connected to the USP-BBP3.7
USP-PROT — Prototyping board: Provides a board for developing and testing custom interface circuits.7
USP-232D — Dual-channel RS232 serial interface: Uses a Z80DART chip and supports baud rates from 75 to 9600, with full handshaking. Supplied with a terminal emulator and a 50-page manual.7
USP-I/O — General-purpose parallel interface: Uses a Z80PIO chip to provide two eight-bit input or output ports with four handshake lines. Supplied with a 30-page manual.7
USP-CENT — Centronics printer interface kit: Adds Centronics-compatible printer connectivity to the USP-I/O, including a cable and software drivers for LPRINT and LLIST.7
USP-PRINT — Packaged printer interface: Based on the USP-I/O board and supplied assembled and tested, with a Spectrum adaptor, cable, comprehensive manual and cassette software.7
The modular design allowed users to combine interface cards according to their requirements and expand the system as additional hardware facilities were needed.7
USP-232D
Dual Serial Interface
USP-ADAP
Adaptor
USP-BBP3
3-slot buffered backplane
USP-BPE4
4-slot back plane extension
USP-I/O
General purpose parallel interface
USP-PROT
Prototyping board
Velleman Interface System
Velleman U.K. Ltd
The Velleman Interface System is a modular interface system for the Sinclair ZX Spectrum, built around the K2616 motherboard. Additional interface boards connect to the motherboard, allowing different hardware functions to be combined without requiring a separate computer interface for each board. Velleman U.K. also imported a corresponding system for the ZX81, using the K2615 motherboard.8
The motherboard connects to the Spectrum through a 23-way edge connector and provides buffered connections for expansion boards. It takes its power from the computer through a voltage regulator, with provision for an external 9V supply if required. The system uses configurable address decoding to help avoid conflicts with other Sinclair peripherals.8
The Velleman interface range included the following boards:
K2609 — Eight-bit output board: Provides eight outputs using transistor switching, with a stated maximum output of 25V at 50mA. An LED is supplied for testing. The instructions include circuit diagrams for connecting a relay or a mains lamp through an opto-isolator.8
K2610 — Analogue-to-digital converter: Converts analogue input signals into digital values.8
K2611 — Eight-bit input board: Provides eight digital input lines.8
K2614 — Centronics printer interface: Connects to compatible parallel printers. Its address decoding follows the same general approach as the output board, with additional printer-control signals and jumpers for configuring non-standard printers.8
K2618 — Digital-to-analogue converter: Converts digital values into analogue output signals.8
The motherboard uses a 23-way edge connector to connect to the computer, while the K2609 output board connects to the motherboard through a 31-way gold-plated connector.8
The accompanying documentation includes large circuit diagrams, construction instructions, explanations of circuit operation and information about address-line allocation to help users avoid conflicts with other Sinclair add-ons.8
The motherboard connects to the Spectrum through a 23-way edge connector and provides buffered connections for expansion boards. It takes its power from the computer through a voltage regulator, with provision for an external 9V supply if required. The system uses configurable address decoding to help avoid conflicts with other Sinclair peripherals.8
The Velleman interface range included the following boards:
K2609 — Eight-bit output board: Provides eight outputs using transistor switching, with a stated maximum output of 25V at 50mA. An LED is supplied for testing. The instructions include circuit diagrams for connecting a relay or a mains lamp through an opto-isolator.8
K2610 — Analogue-to-digital converter: Converts analogue input signals into digital values.8
K2611 — Eight-bit input board: Provides eight digital input lines.8
K2614 — Centronics printer interface: Connects to compatible parallel printers. Its address decoding follows the same general approach as the output board, with additional printer-control signals and jumpers for configuring non-standard printers.8
K2618 — Digital-to-analogue converter: Converts digital values into analogue output signals.8
The motherboard uses a 23-way edge connector to connect to the computer, while the K2609 output board connects to the motherboard through a 31-way gold-plated connector.8
The accompanying documentation includes large circuit diagrams, construction instructions, explanations of circuit operation and information about address-line allocation to help users avoid conflicts with other Sinclair add-ons.8
References
1.
"BASICare PERSONA advertisement listing the ZX81 and Spectrum interfaces, expansion modules and prices.", Sinclair User, No. 16 (July 1983), July 1983, p. 40-41
↩
2.
"THE TOWER OF POWER" - Review of the BASICare expansion system, its modules, memory paging and operation with the ZX Spectrum., Your Spectrum, No. 3 (May 1984)
↩
3.
"7 REASONS TO GO MICROFRAME" - Gordon Microframe advertisement, Your Spectrum, No. 14 (May 1985), p. 42
↩
4.
"Spectrum and ZX-81 Mukbus" - Microtext (U.K.) Ltd advertisement., Sinclair User, No. 17 (August 1983), p. 46
↩
5.
"In Brief - RAM Units" - Brief editorial entry describing the Specspansion four-slot motherboard and 24-line bidirectional programmable port board. Notes the programming-aid cassette and planned additional interface cards; the product is identified as untested by the magazine., ZX Computing, No. December 1984 / January 1985, p. 91
↩
6.
"F B tronics Specspansion advertisement", Sinclair User, No. 19 (October 1983), pp. 125, Programming-aid cassette
↩
7.
"ZX Spectrum expansion - start with one card extend up to seven cards!" - Advertisement promoting the USP ZX Spectrum expansion system from U-Microelectronics., Personal Computer News (PCN), No. 18 (13 July 1983), p. 45
↩
8.
"Instructive links" - A technical review of Velleman U.K.'s modular interface system for the Sinclair ZX Spectrum and ZX81. The article describes the motherboard architecture, power supply arrangements and address decoding, with detailed explanations of the K2609 eight-bit output board and K2614 Centronics printer interface. It also discusses the quality of the construction instructions, circuit diagrams and guidance for avoiding address conflicts with other Sinclair peripherals, and gives prices for the motherboard and two interface boards., Sinclair Projects, No. August/September 1984, p. 5
↩
9.
"VELLEMAN-KITS" - Velleman U.K. advertisement listing interface kits and prices for the Sinclair ZX Spectrum and ZX81, including the K2616 motherboard and K2609, K2610, K2611, K2614 and K2618 interface boards., Radio & Electronics World, No. July 1984, p. 20
↩
Page Revised: 25/10/2026