Ericsson 4187 Plus - Manual (Page 76)

Other Useful Features
Dialog 4187 Plus 76
Hot line
Ask your system administrator if you require this feature.
Delayed Hot line
When the handset of the delayed Hot line phone is lifted, a Call
Duration is started. If no digit is pressed before time out, a call is
automatically generated to a specific extension or external line. If a
digit is pressed before Time out, the phone works as an ordinary
phone.
Direct Hot line
The same feature as described above, but with no delay. Only Hot
line calls can be placed from this line. To be used e.g. as alarm
phone, door phone etc.
Emergency mode
In the event of an emergency, the operator can set the telephone
system into Emergency mode, during which only preprogrammed
extensions are permitted to make calls.