Most second-generation units built by British Rail were designed to use the BSI multiple working system, including members of the 14x Pacer and 15x Sprinter families. Some post-privatisation trains such as the Class 168, 170 and 172s were fitted with BSI couplers enabling them to operate in multiple with older stock, while other incompatible systems emerged.
British Rail's second-generation units, including the Pacer and Sprinter families, were designed for use with the British Standard Interlocking (BSI) multiple working system. Some post-privatization trains like the Class 168, 170, and 172s were equipped with BSI couplers to enable them to work alongside older stock, while other incompatible systems arose.