Nitsuko Digital System DS Administrator's Manual page 146

Operator Assistance
To call into the system
using Operator
Assistance:
Understanding Related Programming
Refer to the DIGITAL SYSTEM Feature and Terminal Programming Manual.
130
Dial system telephone number.
1.
After OPA answers your call, dial announced option:
2.
Dial single-digit option.
OR
Dial 3 plus the extension number you wish to reach.
DIGITAL SYSTEM Administrator's Guide