Disconnection From Supply Source - Keysight E4990A Installation Manual

Introduction
Starting the E4990A
Step 2. Next, if necessary, turn OFF the power supply to the power cable receptacle
(Line Switch) on the rear panel.
Under normal use, never d irectly interrupt the power supply to the power
cable receptacle on the rear panel when the power supply is turned ON.
Always keep the Line Switch ON and never turn it.
If you directly interrupt the power supply to the power cable receptacle
when the power supply is turned ON, or turn OFF the Line Switch, the
shutdown process will not work. This could damage the software and
hardware of the E4990A and lead to device failure.
Turning ON the power supply after a faulty shutdown may cause the
system to start up in a condition called "safe mode." If this occurs, first
shut down the system to set it to the standby state and then turn ON the
power supply again to start up the system in normal mode.
Figure 1-4 Line switch (Always ON) and power cable receptacle

Disconnection from Supply Source

The power supply of the E4990A is cut off by disconnecting the plug of the
power cable (on either AC outlet side or E4990A side). When it is necessary to
disconnect the power supply in order to avoid shock hazards, etc., pull out the
power cable plug from either the AC outlet side or the E4990A side.
20 Keysight E4990A Impedance Analyzer