Tadano Data Transmitter DCU2 and VCU (GR-300EX - GR-1000XL) description of the catalogue:

Crane models
GR-1000XL-3 Mitsubishi, Cummins Tier 4F
GR-750XL-3 Mitsubishi, Cummins Tier 4F
GR-550XL-3 Mitsubishi, Cummins Tier 4F
GR-350XL-3 Cummins Tier 3, Cummins Tier 4F
GR-800EX-3 Mitsubishi
GR-600EX-3 Mitsubishi
GR-500EX-3 Mitsubishi
GR-300EX-3 Cummins Tier 3

This service manual covers the data transmitter (DCU2 and VCU) system installed on the rough terrain cranes (GR).
"Input/output signal of system" in this manual explains the overview of electric circuit of the applicable crane.
For the detailed electric circuit, refer to the service manual (Circuit diagrams and Data) for each model.
In undertaking repair, refer to the separate operation manual, parts catalog, and service manual for each model, and then perform appropriate repair and service.
If the parts replacement is required, check the disassembly and order units from the applicable parts catalog.