I got a second hand Zonet KVM3322 (USB switcher). There's supposed to be a keyboard hotkey combination that can be used to switch between the two attached computers (instead of manually click on the appropriate button on the device). I cannot find the manual online that would tell me what the hotkey combination is.
The default button for many KVM switches is double tap
scroll lock
An alternative can be double tap
ctrl
, but I haven't seen that been used that many places.