Trains operate on typical Indian Railways automatic signalling technology. A Route Relay Interlocking System has been provided at New Garia depot and Tollygunge depot and Electronic Interlocking has been provided at Noapara depot to facilitate the prompt withdrawal and injection of rakes and to perform shunting operations inside the car shed for maintenance purposes. The Train Protection and Warning System (TPWS) is provided throughout the Metro Railway. It is designed to prevent collisions caused by human (operator) error. A Train Describer System and Auto Train Charting are used to help the operation control centre monitor and plan train movement on a real-time basis. An Integrated Power Supply System and Microprocessor based Data Logger System have also been provided. An integrated system of STM-1 and STM-4 optical fibre cable is used for all telecommunication, signalling, SCADA and other circuits in Line 1. The service is provided by RailTel.