The phones need to be configured with a number of conference codes. The main conference code required is one to conference the phones current and held calls. This needs to be set to match a conference add short code on the IP Office system (the default system short code is *47).
The analog B149/B159 phones also need to be configured with codes to send a hook flash to hold/unhold calls.
To set the conference codes:
1.Press the 
Menu button.
2.Scroll to CONF GUIDE and press OK.
3.Scroll to SETTINGS and press OK.
4.At the ENQUIRY prompt enter F and OK. Enter F by pressing the 
key. Backspace by pressing 
.
5.At the CONFERENCE prompt enter F and the IP Office conference add short code, for example F*47. Press OK.
6.At the RETURN prompt enter F and press OK.
7.To exit the menus, press Menu again. To exit the current menu option, press .