An open filament on an auto-alarm with a...

🔍 Key Concepts

• Auto-alarm system sequence: how a fault (like an open filament) is sensed and how the system responds step by step • Function of relays K-100, K-105, and K-106 in a typical fire or alarm auto‑alarm circuit • Difference between a detector fault (like open filament) and a true alarm condition and how each one should affect bells and time delays

💭 Think About

• Think about what an open filament in a linear detector actually means electrically: is the circuit open or closed, and what does that do to the restoring or supervising relay (K-105)? • In a properly designed alarm system, should a detector fault immediately cause the time-delay relay (K-100) and the bell relay (K-106) to operate as if there were a real fire? Why or why not? • Look at the logical order of operations: which relay must change state first when a fault occurs, and which components (time delay, bell) are supposed to respond only to a valid alarm signal?

✅ Before You Answer

• Verify which device is supervising the detector circuit (often a restore/supervisory relay like K-105) and what happens to it when the detector goes open-circuit. • Confirm whether K-100 (time delay relay) is triggered by a real alarm condition or by a fault such as an open filament. • Check if the bell relay K-106 is intended to respond to detector faults, or only after a confirmed alarm signal passes through the time-delay stage.

An open filament on an auto-alarm with a linear detector and an electronic selector will:

De-energize the restore relay K-105

K105 applies voltage to K-100, time delay relay

K106 causes the bell to ring after about 2 minutes

All of the above

🔍 Key Concepts

💭 Think About

✅ Before You Answer