Anritsu 681XXC - Manual (Page 24)

Standby
Operation Whenever the signal generator is not being used it
should be left connected to the power source and
placed in standby. This keeps the internal timebase
frequency reference at operating temperature.
On the front panel, press LINE to switch the
681XXC from OPERATE (green LED on) to
STANDBY (orange LED on).
NOTE
During standby operation, the fan runs
continuously.
681XXC OM 2-5
PREPARATION
INSTALLATION FOR USE
LINE
OPERATE
STANDBY
SYSTEM
MODULATION
LEVEL
CONTROL
Line
Key
Line Voltage
Selector Switch
Line
Fuse
GPIB
Connector
Figure 2-1. Signal Generator Rear Panel showing Power Connection