 The Delhi Metro uses cab signalling along with a centralised automatic train control system consisting of automatic train operation , Automatic Train Protection and automatic train signalling modules . A 380 MHz digital trunked TETRA radio communication system from Motorola is used on all lines to carry both voice and data information . For Blue Line Siemens Transportation Systems has supplied the electronic interlocking Sicas , the operation control system Vicos OC 500 and the automation control system LZB 700 M. An integrated system comprising optical fibre cable , on @-@ train radio , CCTV , and a centralised clock and public address system is used for telecommunication during train operations as well as emergencies . For Red and Yellow lines ALSTOM has supplied signalling system and for line Green and Voilet Bombardier Transportation has supplied CITYFLO 350 signalling system . 
