초록 ▼

Apparatus for monitoring opening of sealed enclosures, especially, but not exclusively, sealed containers containing goods-in-transit, such as goods vehicles, maritime containers or transport containers of the kind carried by tractor-trailers, ships, trains or aeroplanes comprises a radio receiver u

Apparatus for monitoring opening of sealed enclosures, especially, but not exclusively, sealed containers containing goods-in-transit, such as goods vehicles, maritime containers or transport containers of the kind carried by tractor-trailers, ships, trains or aeroplanes comprises a radio receiver unit having at least one antenna for reception of radio signals. The receiver unit is housed within the enclosure and operates to scan a predetermined band of radio frequencies, periodically or continuously, and detect a sudden change in signal level. When it detects such a change in radio signal level, the receiver generates an alarm signal. Alternatively, the receiver may detect the difference between internal and external radio signal levels and determine the container to have been opened if the difference is less than a preset threshold. The receiver unit may be arranged to capture the FM frequency spectrum pertaining when the opening occurred and store it for later comparison with known FM frequency spectra of various cities to identify the location of the enclosure when opening occurred.

대표청구항 ▼

[ What is claimed is:] [1.] Apparatus for monitoring opening of an electromagnetically shielded enclosure, comprising a radio receiver unit having at least one antenna for reception of radio signals, the receiver unit to be housed within the enclosure and comprising means for scanning a predetermine

[ What is claimed is:] [1.] Apparatus for monitoring opening of an electromagnetically shielded enclosure, comprising a radio receiver unit having at least one antenna for reception of radio signals, the receiver unit to be housed within the enclosure and comprising means for scanning a predetermined band of radio frequencies, periodically or continuously, and detecting a predetermined radio signal level; and means operable in dependence upon such radio signal level detection to generate a signal indicating opening of the enclosure.