On the basis of the standard wagons EW1 with bellows and a driver's cab of the type ABDe4/8, six control wagons Bt were delivered to the BLS by the Swiss wagon factory Schlieren (SWS) in 1963. In 1970, 3 more of these control coaches were delivered to the BLS on the basis of the modernized EW1 with rubber bulge and extended wagon body. The control wagon was used, among other things, in shuttle trains. From 2005 on, four converted control coaches with the new numbers BDt 946-949 were in use with car trains and the Bt 951-953 were modernized with outer swing doors in the swing trains.This text is machine translated.