Vertical Communications DSU II - Manual (Page 24)

Redialing
The system temporarily saves the first 16 digits of the last manually dialed number
for your redial use—if the last number you called is busy or is not answering, you
can redial it once or initiate repeated redialing. Subsequent dialing activity
overwrites a temporarily saved number.
· To redial the last-dialed number,
1. LIFT handset OR DISCONNECT current ringing or busy tone.
2. DIAL
#
.
3. LISTEN for ringing or busy tone over the telephone.
18 Single Line Proprietary Telephone Station User’s Guide
Making Calls GCA70-246