Cab Secure Radio

Cab Secure Radio (CSR) was an in-cab analogue radiotelephone system formerly used on parts of the British railway network.

CSR was replaced by the GSM-R digital system, forming the initial phase of rollout of ERTMS throughout the UK.

However it wasn't until the Clapham Rail disaster and subsequent Hidden report also followed by the accident at Cowden where the real value of the facility was learned.

Occasionally the radio failed to change channel or lost the signal completely, in which case the driver could enter the code manually.

[1] The signaller was provided with a visual display unit, specialized keyboard with unique function keys, telephone handset and loudspeaker.