This simple circuit made up of a source,a load and two wires is seldom,if ever,met with inpractice.Practical circuits may contain a large number of sources and loads interconnected in a variety of ways.这种由一个电源、一个负载和两根导线组成的简单电路，在实践中即使能碰到也是很少见的。
实际电路可能包括许多按不同方式连接的电源和负载。
The direct ion of curre nt flow may be show n either by a hollow arrowhead or by suppl ying the curre nt symbol with a double subscript whose first digit identifies the junction at a higher potential and the second 省略了identifies) the junction at a lower potential.电流的方向既可用一个空心箭头来表示，又可用带有双下标的电流符号来表示，且第一个下标认定为高电位点，第二个下标为低电位点。
In a pote ntial-distributi on diagram it is represe nted( on a suitable scale)by the slope of the respective curve at any poi nt,the slope bei ng defi ned as the tangent of the angle that the line tangent to the curve at that point make with the x-axis.在电势分布图中，电流由曲线上该点相应的斜率表示，斜率定义为切线与x坐标轴夹角的正切。
It follow that the r.m.s.(effective) value of an alternating current is numerically equal to the magnitude of the steady direct curre nt that would produce the same heat ing effect in the same resista nee and over the same period of time.由此得出：交流电流的均方根(有效值)大小上等于在相同电阻上和同一时间内产生相同的热效应的恒稳直流电流。
The operational voltage amplifier is representedschematically by the triangular symbol .AO is the voltage gain from differe ntial in put to sin gle-e ndrd output and is always a positive nu mber . Phase reversals are taken into account at the in put termi nal，which is the reas on why these are labeled ” +” andThe voltage at each terminal，including the output ,may be referred to common reference ,usually ground ,and uni ess otherwise stated ,this com mon refere nee will be assumed . Thus ,lett ing V(+) represe nt the voltage of the positive in put term inal with respect to the com mon refere nee ,and V(-),that of the n egative in put term inal ,we may defi ne the differential input voltage as V二V( ) -V (-) ,and the output voltage is V0 = A0V id.电压运算放大器可用三角形符号来表示。
A0表示从差动输入端到单一输出端的电压增益，并恒为正值。
考虑到在输入端可能会有反相输入的情况，所以要标上“ +号与号。
每个端口包括端口的输出端口的电压，都可以选一个共同的参考点，通常选大地，除非另有说明，否则所假定的参考点就是地。
这样，用V(+)代表正向输入端对参考点的电压，而V(-)则代表负向输入端对参考点的电压，我们可以将差动输入电压定义为％二V「)-V(-)，输出电aa压V。
二Ay。
The significance of this result is that the terminal voltage gain ,which is the usable voltage gain , is in depe ndent of the parameters of the amplifier ,and depe nds only on the exter nal comp onent R1 and这个结论的意义在于端电压增益(这是很有用的电压增益)与放大器的参数无关，而只取决于外部元件R1和R2。
A truth table is a list of all of the possible in put variable state combinations of a circuit listed in binary-sequential order with the corresponding output state for each combination listed in an adjace nt colu mn. Tablei shows the binary nu mbera corresponding to the decimal nu mbers from zero to fiftee n.真值表是这样的一个表格，电路中可能输入的所有不同状态组合按二进制顺序连续排列，输出状态与输入端的每种组合--- 对应，表1表示了与十进制0~15 ------------ 对应的二进制数。
The truth table is used as the begi nning point in desig ning or an alyz ing a logic circuit The sequential listing makes it easy to recog nize if any in put comb in ati ons were missed. It is made up of either from the problem specificati ons or by seque ntial testi ng of an assembled circuit. A logic equati on can be formulated from the truth table and a logic circuit can be developed from the equation. Truth tables areused in defining the basic AND,OR and NOT functions below在设计或分析一个逻辑电路时，首先要列写真值表。
这种连续的表格很容易辨认出是否遗漏了任何一种组合，她可有问题的具体情况或对一集成电路进行连续测试来建立。
由真值表可建立逻辑等式，由此等式就可构造一逻辑电路。
在下面定义基本逻辑与”、或”和非”的函数中就用到了真值表。
The logic AND fun cti on can be expa nded to any nu mber of in puts ,simply by appl yin gthe basic defi niti on. Thus a 5-i nput logic AND gate will produce an output only if the in put comb in atio nABCDE=11111 exists,and providing the physical circuit will still function properly with that many in put attached.只要运用基本定义，逻辑与函数便可扩展到任意一个输入。
因此一个五输入的逻辑与门只有在ABCDE=11111且具体电路与那些连接的输入量有恰当的函数关系时才等于一。
Today moti on con trol is an area of tech no logy that embraces many diverse discipli nes,such as electrical mach in es,power semic on ductor devices, conv erter circuits,dedicated hardware sig nal electronics,control theory,and microcomputers,more recently,t he advent of VLSI/ULSI circuits and sophisticated computer-aided desig n tech niq ues has added nel imen sio ns to the tech no logy.当今世界的运动控制是这么一个综合性的技术领域，其包括诸如电机、电力半导体装置、转换器电路、专门的硬件信号电子学、控制理论、微型计算机等方方面面的众多技术领域。
最近出现的超大规模集成电路，甚至特大规模集成电路，再加上日渐程序的计算机辅助设计技术出现，又进一步拓宽了运动控制技术领域新的运用范围。
Mechanical motion control systemS ound widespread acceptanee in industry since the invention of the steam engine started the first in dustrial revoluti on in eightee nth cen tury,whe n mass in dustry manu facturi ng replaced manu al labor.18世纪蒸汽机的发明开启了第一次工业革命，当时大规模的工业生产化代替了手工劳动，从此以后，运动机械的运动控制系统便在工业领域得到广泛地应用。