Excludes Railroad Signals.
Includes Railroad Gates; Flasher Lights; Block Signals.
Excludes Semaphore Flag Signals.
Includes Oxygen Pressure Signals and Warning Devices; such as Air Pressure Warning Signals, Aircraft Crew Warning Signals, Altitude Warning Signals, Alarm Controls, Audible Landing Gear Alarms.
Excludes Aircraft Engine Oil and Fuel Warning Devices.
Includes Anti-intrusion Alarm Systems; Foghorns; Gongs; Chimes; Bells; Burglar Alarm Systems; Fire Alarms; Police Alarm Systems; Sounding Devices; Manual Gas Alarms; Landing Wands; Security Inspection Systems
Excludes Loran; Radar; Sonar; Engine Oil and Fuel Warning Devices; Aircraft Oxygen Warning Devices.