EXTENSIBLE AND RETRACTABLE BARRIER

摘要

A continuous strip of coiled material is provided with protrusions, such as barbs, which are oriented to eliminate mutual interference when the coiled material is stacked in a compact, collapsed nested condition and wherein each turn of the coil is permanently fixed at equiangularly spaced multiple points alternately to its adjacent trailing and leading turns of the coil. An intrusion detection system signals intrusion into the space encompassed by the above mentioned coil and features a microwave energy source, receiver and detector for indicating a reduction in received microwave energy at the receiver indicative of intrusion into or other disruption of the energy guided path determined by the coil. Another embodiment of the barrier provides for similarly barbed strip material provided in a series of linear lengths with each length reversely folded at a succession of fold points to provide a sawtooth profile with the fold points permanently fixed alternately to corresponding fold points of adjacent trailing and leading strip lengths.