One monitor on a twin output system?

[Hodgkinson]

Or, if your monitor as a VGA and DVI input, get an adaptor for the DVI port and use the monitor as the switch ;-)

[Hodgkinson]

There are internal relay-switcher cards around for Amigas, but they need a control signal derived from a suitable signal pin on a graphics card or similar setup (C64 3D Gfx card, for example).

Apart from that it's a pain when it gets it wrong (Ie. Program displays via Scandoubler rather than Gfx card and switcher stays selected to Gfx card...) - A manual override is a useful thing to have.

Hodgkinson.