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Fire rescue is all-weather and all-time. Using rope rescue technology to carry out rescue operations is one of the efficient and convenient methods adopted by firefighters. Grab knots are an important part of this field. This article introduces typical grab knots such as Prusik knot, French knot, Klemheist knot and uses 10.5mm and 12.5mm as main ropes, 6mm, 7mm and 8mm as auxiliary ropes and related equipments in rope rescue to carry out parallel tests by using tensile testing machine. It can be found that the larger the diameter of rope, the greater the maximum tensile force the grab knot will bear. The larger the diameter difference between the main rope and auxiliary rope, the smaller the sliding distance is, and the force effect can be better. Those three types of grab knots have different characteristics and should be selected according to the actual situation. Relatively speaking, the Prusik knot is more suitable for fire rescue. It is hoped that it will help to improve the firefighters’ understanding of typical grab knots, and play a certain reference value for the safety assessment, so as to ensure the scientific and safety of rescue operations.

The fast capture of spread spectrum code is one of the key technologies of Direct Sequence Spread Spectrum (DSSS) communication. There are several traditional methods for the fast capture such as XFAST and AVERAGE. In this paper we propose a new algorithm based on the time domain samples and Binary search according the autocorrelation of the PN code. Firstly, signal's simple rate is reduced to a quarter of the chip rate with the received spread spectrum, and determined with a specific method, then the signal is divided into four parts by the local PN code and accumulated to a new sequence. Finally, the synchronous pseudo-code is captured with the correlation of the two new reference sequences. Experimental results demonstrate that the proposed algorithm significantly improves the efficiency in the capture of long Pseudo-Code code in DSSS, compared with traditional methods.