Class 380 – CCTV System Intermittent Video Loss
Executive summary
This report consolidates the 2021 TP Matrix findings with the SET 2025 Investigation.
The key advancement is the discovery and verification that JetView activation depends on the Remote Data Access (RDA) unit messaging on the CCTV subnet.
By capturing those messages on the train and emulating them with a custom RDA emulator, we achieved full bench activation of the DOO CCTV path, from the camera to Xebra, through JetSwitch, and onward to the JetView displays. This removes the JetView as a root cause and refocuses fault-finding on the Xebra DVR and its handling of video and network data when exposed to railway interference.
Reported Issue
Drivers reported intermittent loss of video on cab displays. Faults were not reported immediately, making timing and replication difficult. Units were typically reported only once the train returned to depot.
Initial Challenge
The CCTV system could not be powered or reproduced directly in the laboratory. Documentation supplied by the customer did not fully describe all system dependencies.
Background
Faulty units were supplied to SET.
Units had previously been investigated by a third party for nearly 6 months – 1 year with no resolution. Third party failed to get working screens to initialise / turn on.
Documentation provided included service manuals and limited internal schematics.
Credit: Scot Rail
Investigation & Reproduction
Full system hardware was requested to allow laboratory replication.
It was identified that coding plugs were required to pair Zebra DVRs to the network switch.
Existing designs were reverse-engineered and improved to manufacture additional coding plugs internally.
Further investigation revealed that the CCTV system will not initialise without configuration data from the RDA (Remote Data Aggregator).
This dependency was undocumented.
Root Cause Identification
On-site depot investigation confirmed that Zebra devices require periodic configuration packets from the RDA.
Missing or incomplete RDA data caused the CCTV system to shut down.
Network traffic was captured and analysed.
A software emulator was developed to recreate RDA configuration packets, allowing full laboratory replication of train conditions.
Fault Replication & Analysis
Once the system was operational in the lab:
Field-failed displays were disassembled and analysed.
Root cause identified as power supply instability, likely induced by EMC events.
Symptoms matched sporadic loss of individual camera feeds rather than total system failure.
Outcome
Full system replication achieved.
Root cause analysis completed.
EMC susceptibility identified, likely affecting Zebra DVR inputs.
Planned mitigation includes ESD and EFT immunity testing and development of input protection circuitry.