The Proface is a keyboard interface for the ZX Spectrum. It supplies the Spectrum with an additional port to connect PC AT-keyboards. It works with Spectrum 16k, 48k, 128k and +2. Without modifying it cannot be used on Spectrum +2A or +3, but it is anyway thought for using mainly on Rubber-key Spectrums.
With an AT/USB Adapter even USB-keyboards can get connected. Such an adapter is not included, but you can still buy it. But still not every keyboard might work, there are differences which makes it incompabtible. However, as easier the keyboards is, as better the chance that it will work.
There are several special keys supported by the interface, so will be classic PC warm-start combination (CTRL - ALT - DEL) cause the wanted reset.
The interface will be connected to the Spectrum rear port, there are no changes of the hardware needed.