Napco RP1016D is displaying an '18', What's that?

[Scott kinney]

This morning my keypad started chirping periodically and displaying
'18'. As far as I can tell in my manual, it should only show 1 - 14 (there
are only 14 zones.) What does an '18' signify?

Thanks in advance,

Scott

 

[Jim Rojas]

I think that means telephone line trouble.

Jim Rojas