Hook flash or
flash (known in the UK as "recall") is a button on a
telephone that simulates quickly hanging up then picking up again (a quick
off-hook/
on-hook/off-hook cycle). This action can signal the
telephone exchange to do something. A common use of hook flash is to switch to another incoming call with the
call waiting service. Another use is to indicate a request for voice conferencing, for example, a user may use a procedure like the following to initiate
three-way calling:
- Pick up phone handset (causing the line to be off-hook).
- Hear a dialtone
- Dial the first number and greet the first party
- Press the hook flash button (or quickly tap the on-hook sensor on the phone)
- Hear a stutter dial tone (a series of beeps followed by another dialtone)
- Dial the second number and greet the second party
- Press the hook flash button again.