The Meter consists of an easily-removable front panel and the rest of the box. 

The box contains the line input, switch, the power supply, Attenuator, and the External Amplifier.

The rear panel contains the IEC input, the line switch the attenuator knob and the reset push-button.

It also contains a switch which, in the up position, connects the external input to the circuit ground. 

The box itself is connected only to line ground.

The input jacks are connected to the attenuator by connector. 

Everything else is connected to  the board containing the Arduino and the Rear Amplifier

by cables with connectors.

However, the RTC plugs into the board directly using a 7-pin header. 

The Mini-Pro is programmed using RS-232 via 6-pin header. An extension cable comes out at the rear.