What is the primary purpose of an 'open collector' in alarm systems?

The primary purpose of an 'open collector' in alarm systems is to create a relay signal. Open collector outputs are a type of digital output that can control a relay or interface with other circuits by allowing current to flow through a transistor when activated. This is particularly useful in alarm systems where the need for triggering an external device or signaling an alert is critical.

When the open collector is activated, it connects to ground, allowing current to pass through a connected load, such as a relay that might activate alarms or other alerts. This design is effective for integrating various devices and creating signals that can manage multiple responses within an alarm system, such as triggering an alert or communicating with other components in the system.

The other options do not align with the functionality of an open collector. Sound amplification, visual alerts, or temperature measurement rely on different mechanisms and components, thus distinguishing the role of the open collector specifically in signal relay capacities within alarm systems.