Aastra 673xi User Manual page 7

Aastra 673xi / 675xi SIP Telephones
Key Extensions
With an Aastra M670i or Aastra M675i key extension the Aastra 6753i, Aastra 6755i
and Aastra 6757i telephones can provide additional function keys:
Aastra M670i: 36 function keys
Up to three key extensions can be connected to designated telephones: three key
extensions of either the M670i type or three of the M675i type. Key extensions
cannot be combined on the OpenCom 1000 communications system:
Key Extension
(up to three) M670i
(up to three) M675i
Note
The Aastra 6730i, Aastra 6731i or Aastra 6751i do not offer key extensions.
Aastra M675i: 20 softkeys respectively
programmable on three levels (total of
60 storage locations)
can be connected to the telephones
Aastra 6753i
Aastra 6755i
Aastra 6757i
Aastra 6755i
Aastra 6757i
3