Signal button
A signal button is a control element on telephone terminals such as telephones or fax machines for controlling special switching functions such as queries, toggling or three-party conferences . The signal buttons are named after their original function, but usually have several purposes, depending on the order and combination in which they are operated:
- Earth button; for control in old analog telephone systems (connects the a-wire to earth when activated)
- Flash button; for control in telephone systems (interrupts a and b wire for 80 ms when pressed)
- Hook flash button; for control in public telephone networks (like flash button, but with longer interruption time, 250 ms)
- R key (inquiry key) is the common name for a signal key with the aforementioned techniques
literature
- Dietrich Arbenz From drum voter to optiset E - The history of wired telephones for Siemens' private branch exchanges (1950–2000) , Herbert Utz Verlag, Munich 2009, ISBN 978-3-8316-0908-6 .
- Hubert Zitt: ISDN & DSL for PC and telephone. Markt + Technik Verlag, Munich 2005, ISBN 3-8272-6987-3 .