3Com V7111 - VCX 4 Channels Analog FXO Media Gateway User Manual page 62

Connect the 8FXO ports directly to PBX lines as shown in the following figure:
8FXS and 8FXO Layout
Figure 28
Dialing from Remote Extension When the Phone Is Connected to a VCX 7111 8FXS
To configure the call, follow these steps:
Take the handset off, to hear the dial tone coming from PBX, as if the phone was
1
connected directly to PBX.
8FXS and 8FXO establish a voice path connection from the phone to the PBX
2
immediately after the phone handset was raised.
Dial the destination number (the DTMF digits are sent, over IP, directly to PBX).
3
All tones heard are generated from PBX (such as ringback, busy, or fast busy tones).
4
There is one-to-one mapping between 8FXS ports and PBX lines.
5
The call is disconnected when the phone connected to 8FXS goes on-hook.
6
Dialing from other PBX line, or from PSTN
To configure the call, follow these steps:
Dial the PBX subscriber number the same way as if the user's phone was connected
1
directly to PBX.
62 3Com VCX V7111 VoIP SIP Gateways User Manual