Holdup alarm initiation devices shall comply with UL ______.

Holdup alarm initiation devices must meet the standards set by Underwriters Laboratories (UL) for safety and performance. The correct answer, which is UL 636, pertains specifically to these alarm systems, indicating that the devices should be tested and certified to ensure they function reliably and are resistant to tampering.

By adhering to UL 636, these devices are evaluated for various factors, such as their ability to respond correctly to unauthorized access attempts while minimizing false alarms. This is crucial for ensuring that holdup alarms provide a reliable means of alerting authorities to potential robbery or other security threats.

The other options refer to different UL standards that apply to various types of alarm systems and devices, which do not specifically address holdup alarms. For instance, UL 632 pertains to police station and fire alarm signaling systems, and UL 634 focuses on specific types of fire alarm components, making them unsuitable for this particular category of alarm initiation devices. Thus, UL 636 is the standard that correctly governs holdup alarm initiation devices.