Address assignment and cryptographic key initialization is sometimes performed by closing a contact on the device while having a master controller broadcast an assignment message.
The train operator must turn the handle of the master controller and keep his or her hand on the handle to release the brakes and deactivate the dead man switch.
The master controller had four positions, switching, full series, parallel, and full parallel, and control equipment shunted out starting resistances automatically as speed increased and current drawn fell.
The unit had been plagued by master controller problems and was only in service for three years before it was withdrawn after maintenance revealed two cracked trucks.