3
Operating instructions
HT 644 - 01
The HT 644-0 is a dialogue-oriented in-house telephone with a display for indication of all actions and
responses. Operating errors and faults are indicated with the message "not possible xx".
XX stands for an error code which is explained in the table on page 7.
Several functionality is only available up from version 4.xx.
SSS
SIEDLE
L1
L2
L3
L4
9
F
1
0
2
3
4
5
6
7
8
i
