Interface 1bis for the Sinclair ZX Spectrum

The device is a functional replica of the Sinclair Interface 1, maintaining full backwards compatibility at BASIC command and hook-code level, yet featuring considerably enhanced capabilities due to its innovative micro-controller based architecture, a solid firmware and time-tested operating system.

The ‘Interface 1bis’ is designed to be connected directly to the expansion port of original Sinclair or Amstrad ZX Spectrum computers or of a Sinclair Interface 1

Unlike most ZX Spectrum add-ons, the IF1bis does not perform hardware trapping and can therefore function even if the host machine's CPU has a faulty /M1 line.

The IF1bis does not rely upon the host machine's CLK line, which on some ZX Spectrum models is unusable.


The user interface, with joystick and mouse control, gives access to all of the the interface's functions, without typing any BASIC commands.


Online game archives can be accessed directly via the internet connection of a PC server linked over USB or an IP network.


About 500 units were assembled and distributed between 2013 and 2020, at a net post-calculated margin of around 80%

The entire project is released in the public domain and can be used by anyone for whatever purpose, without any restriction, obligation or acknowledgment.

More information, the full hardware documentation and source code may be requested contacting the author at the G(oogle)mail address: antohi<dot>dan.