Merlin 3070 Service And Maintenance Manual page 247

Turn the control unit power off. If you have an auxiliary power supply,
2.
unplug the auxiliary power cord from the control unit before inserting
the 2-Line/5-Voice Terminal Module (Figure 3).
Power Switch
Locate the leftmost available module slot.
3.
4. Grasp the handle on the faceplate of the module slot and pull it open
(Figure 4). Do not remove the faceplate.
Figure 3.
Removing the Auxiliary Power Cord
Faceplate
Figure 4.
Opening the Faceplate
Auxiliary Power Cord
Locking Tab