alarms should be connected to a b.t 92 a after nte
A 92a is a redcare block, but I know what you mean, there are many variants that can be used but where broadband exists the best method is connecting directly to the screws on the back of the NTE5 ( if it exists ) and then using a filtered block to change to the alarm wire.
This is to prevent the alarm being unplugged, even by someone removing the front plate of the NTE5.
An alternative would be to use the NTE2000 and connect the cable going to the alarm to the filtered terminals, this does however leave the possibility that someone could leave the front plate off after testing etc and cause the alarm dialler to be disconnected.