code/game/machinery/datanet/p2p_phones/_p2p_phones.dm

STATE_WAITING	Idle
STATE_ORIGINATE	Calling remote station
STATE_ANSWER	Being called by remote station
STATE_CONNECTED	Call active
STATE_HANGUP	Far side hung up
STATE_FARBUSY	Far side busy, Temporary state
HANDSET_ONHOOK	Handset is on the phone.
HANDSET_OFFHOOK	Handset is off the phone, but still around
HANDSET_MISSING	Handset missing or in invalid state

Define Details

Handset missing or in invalid state

Handset is off the phone, but still around

Handset is on the phone.

Being called by remote station

Call active

Far side busy, Temporary state

Far side hung up

Calling remote station

Idle