B4 bogie, and a comfortable ride could then be relied on, as was evident in the later EMU vehicles. An important factor was the compressive coupling, which provided excellent inter-vehicular damping through the gangway end-plates, which quickly became highly polished, indicating that they were performing this task. A device known as a tell-tale connects the emergency (communication) cord or chain to the train line to facilitate an emergency stop. Sleeping cars British Railways and outside contractors built the British Railways Mark 1 sleeping car between 1957 and 1964. Three hundred and eighty cars of three different types were built, with a fourth type created later by conversion. None remain in front-line service and very few are preserved (this was due to asbestos insulation in most carriages). Three types were designed, based on the BR Mark 1 underframe and profile. All featured 11 compartments with side corridor, an attendants' pantry at one end, and two toilets at the other. There was one fixed berth in first class compartments and two fixed berths in second class. Thus the Sleeper First (SLF) slept 11 and the Sleeper Second (SLSTP) 22. The Sleeper Composite (SLC) had five first class and 6 second class compartments. Early examples were fitted with BR1 bogies which were later replaced with B5 bogies. Later examples were fitted with Commonwealth bogies from new. The cars weighed 39 to 42 tonnes, with the First-class cars weighing one tonne less than the others, and cars with the fabricated B5 bogies also weighing one tonne less than those with the heavy cast steel Commonwealth bogies. Modifications In order to overcome the lack of flexibility in the fleet of sleeping cars, Wolverton works modified some of the SLSTP cars with a stowable top berth. The resulting Sleeper Either class with Pantry (SLEP) cars could then be used to better accommodate the fluctuations in passenger demand. The SLEPs were renumbered in the 2800-series. Replacement The Mark 1 sleeping cars fleet continued to serve British Rail for many years. With no Mark 2 sleeping car design, the Mark 1s continued until the British Rail Mark 3 sleeping cars entered service in the early 1980s. 1957 prototypes In 1957 a dozen carriages were built: four by Doncaster Works and two each by four outside contractors, in an attempt to improve on the existing design. While the passenger comfort level may have improved, the passenger capacity fell (except