A genuine U.S. Vietnam War AN/GSQ 171 directional infrared intrusion detector & sensor. Made specifically for the Vietnam War as the manufactures plate shows both English & Vietnamese text. Over twenty of these infrared intrusion detectors could be connected to a radio receiver, when set-off by an intruder the detector would send a signal to the radio receiver to let the operator know exactly what era has been breached. This large metal cased detector is numbered #23 on the top. It retains its aerial which is often missing or broken, and includes the sensor that connects to the detector. The detector measures: 310mm x 90mm x 210mm (12.2" x 3.5" x 8.2"). Scarce item.