FSC 6310

Excludes Railroad Signals.

FSC 6330

Includes Railroad Gates; Flasher Lights; Block Signals.
Excludes Semaphore Flag Signals.

FSC 6340

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.

FSC 6350

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.