20世纪30年代中后期始有标志飞行场地或跑道边界的灯具。
1953年以后，大型快速的涡轮螺旋桨飞机和喷气式飞机相继问世，驾驶员需要在更远的地方发现跑道，航空运量的不断增长也对飞行安全和航班正常提出了更高的要求。
二、产品执行标准GB三、使用特性1、交流额定电压：U0/U450/750V；2、最高工作温度：阻燃聚氯乙烯绝缘和护套70℃和105℃；氟塑料绝缘和护套200℃和260℃；交联聚乙烯绝缘90℃；低烟无卤阻燃聚烯烃70℃；低烟无卤阻燃交联聚烯烃90℃和125℃。
This company produces the type refractory power cables for rated voltage 0.6/1 kv copper core cable, can also produce low smoke zero halogen fire-resistant power cable, high flame retardant fire-resistant power cable oxygen insulation layer, the fire-resistant performance in line with the GB/T12666.6 cable fire resistance test method. Therefore, the overall performance of refractory series power cables is good and reliable. The water resistance performance of fireproof cable conforms to iec 502-2.
Forlayingindoors、intunnel,cabletrench,ordirectinground,abletobearexternalmechanicalforces,butunabletobearlargepullingforce。
这样本公司的交联聚乙烯电力电缆的整体水平低于国内领先地位。
本公司生产的耐火型电力电缆为额定电压0.6/1KV铜芯电缆，还可以生产低烟无卤耐火电力电缆、高阻燃隔氧层耐火电力电缆，其耐火性能符合GB/T12666.6《电线电缆耐火特性试验方法》。
PLC与PLC之间的通信。
通信的基本类型：并行通信与串行通信并行通信:是将一个数据的每一个二进制位，均采用单独的导线进行传输，并将发送与接收方进行并行连接；如下图所示串行通信：是通过一对连接导线，将发送与接收方进行连接，传输数据的每一个二进制位，按规定的顺序，在同一连接导线上，依次进行发送与接收。
如下图所示：PLC的通信一般都是用串行通信。
标准串行接口用于通信线路连接的输入/输出线路称为接口。
连接并行通信线路的称谓并行接口；连接串行通信线路的称谓串行接口。
产品具有较强的电磁干扰、抗雷击及均衡电位、改善供电品质的特性，特别适宜计算机中心、航空航天监控中心、智能大楼等精密电子装置的场所。
■执行标准企业标准■使用特性1、导体的直流电阻参照聚氯乙烯绝缘及护套电力电缆2、交流电压试验成品电缆经受交流50HZ、5min、3500V的试验电压不击穿，对于单芯电缆，应进行浸水耐压试验。
Total shielding DJYVPDJYPVDJYPVP polyethylene insulation PVC sheathed electronic computer cable group polyethylene insulation shield PVC sheathed electronic computer cable polyethylene insulation group total shield PVC sheathed electronic computer cable 1, fixed for laying indoors, in cable trench or pipe 2, cable long-term working temperature: - 20 ℃ + 65 ℃, the cable laying temperature not lower than 0 ℃, the bending radius should not less than 10 times of cable diameter DJYVPR DJYPVR DJYPVRP polyethylene insulation total shield PVC sheathed computer with a soft cable group polyethylene insulation shield PVC sheathed computer with a soft cable polyethylene insulation group total shield PVC sheathed computer with a soft cable shows that: (1) flame retardant cable (oxygen index greater than 30) need to add code "out" in front of the model. For example, zr-djypv zr-djypvp et al. (2) armored (steel belt armored) cables need to add code "22" in the lower right corner of the model, such as: DJYPV22 djypvpppvp22, etc. This cable is mainly used for ac or dc 300V and below working system, it can work normally when 500V or below.
Tianjin Siemens: bus cable; Profibus DP cable.2 core purple cable, aluminum foil and metal wire braided double-layer shielding, solid bare copper conductor, 2 core in pairs, red and green core wire, green PVC outer sheath, purple appearance. Profibus DP cable adopts solid bare copper conductor as core wire, thickened aluminum foil and encrypted bare metal wire braided layer, good shielding effect, purple PVC outer sheath. Good transmission performance. ? 6xv1830-0eh10 L2 cable 2-core shielding (PROFIBUS bus bus bus cable) tianjin Siemens (original 6xv1830-0ah10 has been upgraded to 6xv1830-0eh10)? VDE 0472; Class B test (IEC332.1). With the rice logo, divided into 100 meters, 200 meters, 500 meters, 1000 meters wooden wheel packaging. Working parameters: single wire transmission large specification: 1000m, with repeater can reach 10000m
1；ZR-KVVRP32多股铜芯、对绞、铜丝编织总屏蔽阻燃仪表信号钢丝铠装电缆1x2x1.5mm2千米6X2X1.5mm20.14X2X1.5mm20.11x2x1.5mm21.212X2X1.5mm22-KVVP32铜芯聚乙烯绝缘聚乙烯护套对绞、总屏。
Flame retardant grade: C for fire temperature: 815 ℃ or higher for fire time: 20 min into a bundle of cable laying nonmetallic material volume: acuity 1.5 litres/m carbonized height: 2.5 meters or less self-extinguishing time: 1 h or less;
HJVVHJVVP0.4-0.8mm5芯-200芯用于配线架至交换机或交换机内部各级机器间连接等（包括农村局用）。
4、使用特性：电缆敷设环境温度不低于-5℃。
电缆的弯曲半径不得低于电缆外经的20倍。
：一台最多可以提供48个千兆端口的交换机，其满配置容量应达到48×1G×2=96Gbps，才能够确保在所有端口均在全双工时，提供无阻塞的线速包交换。
包转发率满配置包转发率(Mbps)=满配置GE端口数×1.488Mpps+满配置百兆端口数×0.1488Mpps，其中1个千兆端口在包长为64字节时的理论吞吐量为1.488Mpps。
：如果一台交换机最多能够提供24个千兆端口，而宣称的包转发率不到35.71Mpps(24x1.488Mpps=35.71)，那么就有理由认为该交换机采用的是有阻塞的结构设计。
DJYDPYD(R)低烟无卤阻燃聚烯烃绝缘和护套铜丝编织分屏计算机用屏蔽(软)电缆。
DJYDPYD(R)P低烟无卤阻燃聚烯烃绝缘和护套铜丝编织分屏总屏计算机用屏蔽(软)电缆。
DJYDYD(R)P2低烟无卤阻燃聚烯烃绝缘和护套铜带绕包总屏计算机用屏蔽(软)电缆。
2 电缆的使用特性、分类与命名2.1 使用特性2.1.1电缆额定工作电压：450/750V、600/1000V。
2.1.3电缆敷设时环境温度应不低于0℃。
2.1.4电缆最小弯曲半径：非铠装电缆：阻燃型为电缆外径的6倍，耐火型为电缆外径的12倍；铠装型电缆为电缆外径的20倍。
4.485布线可以任意布设成星型接线与树形接线。
485布线规范是必须要手牵手的布线，一旦没有借助485集线器和485中继器直接布设成星型连接和树形连接，很容易造成信号反射导致总线不稳定。
很多施工方在485布线过程中，使用了星型接线和树形接线，有的时候整个系统非常稳定，有的时候则总是出现问题，又很难查找原因，一般都是由于不规范布线所引起的。
Flame-retardant cable: the electric wire and cable are produced by external heating. In order to achieve the purpose of flame retardant, the three elements must be caused, namely, combustible gas, heat and oxygen. Therefore, generally USES is added in the sheath material containing halogen halide and metal oxide, from the perspective of flame retardant, that's very good, but, because of the halide is contained in these materials, in a lot of smoke and released when halogenated body, so, the low visibility when fire, bring a lot of personnel evacuation and fire obstruction, whereas people more for functioning suffocated to death.