What is the difference between an intrusion detection system and an alarm?

• A. IDS monitors for unauthorized access using sensors; an alarm notifies security staff when triggered.
• B. IDS triggers internal alarms only; an alarm never notifies staff.
• C. IDS replaces human guards; alarms are manual.
• D. IDS only monitors video footage; alarms manage access cards.

Answer: (A)

The difference being tested is between detecting an intrusion and signaling responders. An intrusion detection system is focused on monitoring for unauthorized access by using sensors—door and window contacts, motion detectors, glass-break sensors, and similar devices—to identify suspicious activity. An alarm is the response that occurs after a detection: it notifies security staff, may alert a central monitoring station, and can trigger automated actions like audible alerts or door lockdowns. So, the best description is that the IDS monitors for unauthorized access using sensors, while the alarm notifies security staff when triggered. In practice these systems typically work together, with the IDS generating an alarm event when it detects something. The other options misstate the relationship: alarms do notify staff; IDS does not simply trigger internal alarms or replace human guards; IDS uses more than just video and is not limited to managing access cards.