NEC Electra Elite IPK II System User Manual page 266

Document Revision 4C
To release Dial Block from another extension:
1. At the multiline terminal, press Speaker.
- OR -
At the single line telephone, lift the handset.
2. Dial 601.
3. Dial the 4-digit Dial Block code.
4. Dial the extension number to be released from Dial Block.
5. Dial 0.
Confirmation tone is heard.

6. Press Speaker or replace the handset to hang up.
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Electra Elite IPK II
Code Restriction, Dial Block