The swing door electric trailer cars were recoded from two main electric trailer classes, _AT_ and _BT_, with some cars being converted from steam hauled cars.
Conversion and recodings took place between 1921 and 1925. For suburban service the T class cars were designated as 'Second Class'.
In 1929, ten trailers were converted back to steam hauled cars.
During 1940/41, fourteen carriages were converted to Second Class use and coded BT. A further fifteen cars were modified to BT class between 1957 and 1968. The T class car numbers were retained.
Between 1953 and 1974 the T class cars were progressively scrapped, with some converted to _WW_ sleeping cars.
The T number group was 1 - 111, 126.