AT&T MERLIN LEGEND Release 2.0 MLX Direct-Line Consoles Operator's Manual page 94

Features
NOTE:
You can change to ES Off only from a console that has
been programmed with this capability. Status cannot be
changed to ES Off from the extension, except in calling
groups.
To Change Extension Status on a
Single-Line Telephone
2. Dial one of the following:
#45 for ES1
#44 for ES2
3. Hang up.
To Change Extension Status on a
Multiline Telephone
1. Press Feature.
2. Dial one of the following:
45 for ES1
44 for ES2
4-26
Extension Status