User`s guide

216 Agilent E6474A User’s Guide
E Permanent In-Vehicle Hardware Installation
Ignition Sense Lead
Connect the ignition sense lead of the power cable to a source
that measures +12 volts only when the ignition switch is on,
using one of the following methods:
Connect it to the radio side of the radio fuse.
Figure 76 Ignition Sense lead connected to the vehicle