Fire alarms not linking in with each other

[Homervanderjazz]

Hi,

so I have two wired fire alarms which use to link in with each other. By this I mean if the downstairs one went off the upstairs one would start ringing as well.

however, this has not been the case for a while now. The downstairs one was changed a number of years ago but from what I recall they did still set each other off for a time.

Anyone have any thoughts on why they no longer set each other off? Thanks

 

[Taylortwocities]

Are they both the same make/model?

 

[Homervanderjazz]

Are they both the same make/model?

No different companies...

 

[flameport]

Devices from different companies won't be compatible.
Replace both of them.