AT&T 7406BIS - Manual (Page 53)

To activate the speaker 1 Press [
Speaker
]
while on the handset
●
The handset will remain active, and the speaker will
also be active. This allows group listening, although
you can still only talk through the handset. Do not
hang up the handset or the call will be dropped
To turn off speaker and 1 Press [ Speaker ]
return to handset only
● The speaker turns off (handset remains active)
To end a call if only the 1 Press [
Speaker
]
speaker is active
(handset on-hook)
To end a call if both the 1 Hang up handset
handset and speaker
are active
● The speaker turns off automatically