Driving Brake Standard Open

A Driving Brake Standard Open (DBSO) is a type of railway carriage in the United Kingdom, converted to operate as a control car; this is not to be confused with DVTs, such as those in InterCity 225 sets. Fourteen such vehicles, numbered 9701 to 9714, were converted from Mark 2F Brake Standard Open (standard class coaches with brake van) carriages.

Source: Wikipedia — Driving Brake Standard Open (CC BY-SA 4.0)