DTMF in-band and out-of-band

DTMF in-band means DTMF tones are sent as audible tones along with the voice (DTMF is sent IN the voice frequency BAND).
DTMF out-of-band means DTMF tones are sent as the numerical value in a packet (RTP type telephone-event, refer RFC2833).
High-compression codecs such as G.729 are designed to carry voice waveforms not tones, so may have problems with DTMF in-band.
You can set your VOIP device either way. Whether out-of-band works depends on your provider also supporting it.

[Call features] Calling Line Identification and Prohibit

Call ID 顯示與隱藏


使用電話按鍵來控制是否顯示Caller ID

Absentee Service

This facility
enables you to attend the calls in your absence. This feature works like a Voice
Mail Service without using answering machine. If you avail and activate this
facility, you will not receive any incoming call on your Phone, the tape will
indicate your absentee to the calling party. During this period, outgoing calls
can still be made as usual. On lifting the handset a different dial tone will be
heard indicating that the Absentee facility is activated. For this service,
calling party's meter will not operate. You can activate or deactivate this
facility using following codes according to your convenience.