Noun
switch hook (plural switch hooks)
Alternative form of switchhook
Either party could "flash" the operator's supervision lamps by depressing their switch hook for a second and releasing it, in case they needed assistance with a problem. Source: Internet
In the United Kingdom, it used to be possible to make calls from coin-box phones ( payphones ) by tapping the switch hook without depositing coins. Source: Internet
However, many telephone makers implemented a slow switch hook release to prevent rapid switching. Source: Internet