''Each button (left, right, button 1 ect.) is in fact a voltage(very small), this voltage is grounded to result in movement, fire, jump ect. For standard master system controllers this is directly feed to the system via wires only (some other controllers use a micro chip) they also are not connected to voltage, while some others do.
''The Sega Genesis (in Europe sold as Sega MegaDrive) pads are an extension to the Sega Master System pads. They use more buttons (3+1, 5+1, 6+1). They use the one usnused pin as a select pin for reading more buttons.''''
Those SMS standard controlers may be used alsmot unchanged on a CPC if the software allows to redefine controls. As a result you may use only one button : the fire 2 wich would be the button 1 on the controller.
The only change is that the button1 (CPC) is button 2 on SMS. but you may use only one button, the use of 2 buttons would need a "re-wiring" solution (a "flexible" modular adaptator may be fine) so it can't always fit unchanged on Plus range.
It seems the "Power" button on SMS controlers is used when the controler is fitted with AutoFire option (needs to be checked) or when using the Lightgun.
But an external adapter may include such power-supply feature too so may works well with some mouses or Lightguns if softwares support thoses.
==Nunchakus technique==