Used by the routines at 30198, 30458, 30575, 30675 and 31244.

Bit(s)	Meaning if set
0	Unused
1	The telephone call is finished (disconnected)
2,3	Unused
4	A digit is being dialled
5	The destination telephone is ringing
6	Sam must give a name in response to 'WHO'S THERE?'
7	Sam has picked up a ringing telephone