Alarm sounds inside but not outside?

Hi Brian,
the internal and external sounders are two separate circuits to each other most likely.
first thing to check is the small glass, low amperage fuse inside the control panel which protects the external sounder circuit. if it has failed then it will need to be replaced. however, if it has failed and fails again then there is a fault to the sounder or more likely the sounder wiring. DON'T BE TEMPTED TO FIT FAILED FUSE WITH SILVER PAPER. FIRE RISK.
GOOD LUCK

MIKE
May 2017