*66: Activates repeat dial until call is picked up or time out
From PhonePower Knowledge Base
Turns On the call connection Busy Feature.
When activated, the last phone number that the user dialed is automatically redialed until the called party is connected or 30 minutes passes.
To use:
Pick up the Phone Power phone.
Once you hear a dial tone, dial *66.
Hang up the Phone Power phone.
When the call connects, your phone will ring and the call will function normally.