Patent ID: 7637556

Claim:
A security system for a truck having a cargo section and a door to access said cargo section, said door having an open and a closed condition, said security system comprising: control means situated on said truck; sensing means for detecting the condition of said door and for conveying to said control means a signal representative of the condition of said door; means situated on said truck for receiving RF signals and for conveying said received RF signals to said control means; alarm means situated on said truck; RF transmission means able to be carried by a person, said RF transmission means having a given RF output power corresponding to a distance within which said RF signal may be received by said RF signal receiving means; said RF transmission means continuously transmitting at regular intervals a digitized RF signal receivable by said RF signal receiving means; said control means comprising means to process said signal representative of the condition of said door, timing means to determine if said RF signal is received by said RF signal receiving means within an interval of time that is within a first time interval, and means for causing said alarm means to emit an audible alarm when said RF signal is not received within said first time interval, and the condition of said door is open.