Vertical Communications DSU and DSU II - Manual (Page 55)

4.5 Waiting For A Line (Queuing)
If all the lines in a line group are busy, you can place your telephone in
a queue to await an idle line in the line group. When you share a line
with another telephone and the line is busy, you can place your
telephone in a queue to await the idle line.
•
To queue for a line group,
1. Press INTERCOM.
2. Dial the line group access code (9, 81, 82, 83).
3. Hear busy tone.
4. Dial ✳ 8 and hang up.
5. When line group is free, your telephone sounds several short ring
bursts. When you hear this, lift the handset, listen for dial tone, and
place call.
•
To cancel line group queuing,
1. Press INTERCOM, dial # 8 and hang up.
•
To queue for a line that appears on your telephone,
1. Press HOLD.
2. Press line button of busy line.
3. Hear short tone.
4. When the line is free, your telephone sounds five short ring bursts
telling you that you can use your line. Lift handset to answer. If
you no longer need the line, ignore the ring burst.
GCA70–245 Making Calls
LCD Speakerphone Reference Manual 4–5