Since the Ei166 alarms have been discontinued, Ei Electronics (also known as Aico in the UK) have designed their new optical smoke alarm to be the perfect, fully compatible replacement. The new alarm can connect with any Ei160 series alarms still in your system, and it will even fit onto your existing Ei166 base without any need for an electrician. The optical sensor technology in the replacement unit has been upgraded to be even less susceptible to false alarms than its predecessor. To make the alarm replacement process as smooth as possible this alarm will be supplied with an easichange replacement tool.