NEC DSX-40 Feature Handbook page 167

To retrieve a line on System Hold at a remote co-worker's extension:
Access the tie line.
1.
2. Dial *4.
Dial the number of the line that is on Hold in the remote system (e.g., 01 for line 1).
3.
DSX Feature Handbook
Tandem Calls / Unsupervised Conference
Hold
Features ◆ 159