The Union (ex Chubb) 3G110 British Standard (BS3621) deadlock works on 5 detainers increasing security. 3G110 is a high security deadlock that conforms to British standard :1998. Union 3G110 5 Detainer British Standard (BS3621) deadlock can be used in conjunction with alarm systems. Note if you are using this with an alarm system then please select the 3G110 with micro switch.