Now let's examine some of the basic instructions is greater detail to see more abOut what each one does.

现在让我们看一些基本的指令，更详细地了解每个指令的功能。

Load / Load指令

The load (LD) instruction is a normally open contact. It is sometimes also called examine if ON (XIO) (as in examine the input to see if its physically ON). The symbol for a load instruction is shown below.

load (LD)指令是一个常开触点。有时也称为检查是否打开（XIO）（就像在检查输入点以查看其在物理意义上是否闭合），load指令的符号如下所示：

A Load (contact) symbol / Load（常开）符号

This is used when an input signal is needed to be present for the symbol to turn ON. When the physical input is ON we can say that the instruction is True. We examine the input for an ON signal. If the input is physically ON then the symbol is ON. An ON condition is also referred to as a logic 1 state.

当需要一个输入信号才能使这个符号闭合（ON）时，就使用这种方法。当物理输入闭合（ON）时，我们可以说指令是“真”。我们检查输入点的闭合（ON）信号，如果输入点在物理上是闭合（ON）的，那么这个符号就是闭合（ON）的。一个闭合（ON）状态也称为逻辑1状态。

This symbol normally can be used for internal inputs, external inputs and external output contacts. Remember that internal relays don't physically exist. They are simulated (software) relays.

此符号通常可用于内部输入、外部输入和外部输出触点。记住，内部继电器在物理上并不存在，它们是模拟（软件）继电器。

LoadBar / LoadBar指令

The LoadBar instruction is a normally closed contact. It is sometimes also called LoadNot or examine if closed. (XIC) (as in examine the input to see if its physically closed) The symbol for a loadbar instruction is shown below.

LoadBar指令是一个常闭触点。有时也称为LoadNot或（XIC）（就像在检查输入点看其在物理意义上是否关闭）。loadBar指令的符号如下所示：

A LoadNot (normally closed contact) symbol / LoadNot（常闭）符号

This is used when an input signal does not need to be present for the symbol to turn ON. When the physical input is OFF we can say that the instruction is True. We examine the input for an OFF signal. If the input is physically OFF then the symbol is ON. An OFF condition is also referred to as a logic 0 state.

当不需要一个输入信号就可以使这个符号闭合（ON）时，就使用这种方法。当物理输入打开（OFF）时，我们可以说指令是“真”。我们检查输入点的打开（OFF）信号，如果输入点在物理上是打开（OFF）的，那么这个符号就是闭合（ON）的。一个打开（OFF）状态也称为逻辑0状态。

This symbol normally can be used for internal inputs, external inputs and sometimes, external output contacts. Remember again that internal relays don't physically exist. They are simulated (software) relays. It is the exact opposite of the Load instruction.

此符号通常可用于内部输入、外部输入，有时也可用于外部输出触点。请再次记住，内部继电器在物理上并不存在。它们是模拟(软件)继电器。LoadBar指令与Load指令完全相反。

*NOTE - With most PLCs this instruction (Load or Loadbar) MUST be the first symbol on the left of the ladder. / *注意：对于大多数PLC，这个指令（Load或Loadbar）必须是梯形图左边的第一个符号。

Out / Out指令

The Out instruction is sometimes also called an OutputEnergize instruction. The output instruction is like a relay coil. Its symbol looks as shown below.

OUT指令有时也称为OutputEnergize指令。输出指令类似于一个继电器线圈，它的符号如下所示：

An OUT (coil) symbol / OUT（线圈）符号

When there is a path of True instructions preceding this on the ladder rung, it will also be True. When the instruction is True it is physically ON. We can think of this instruction as a normally open output. This instruction can be used for internal coils and external outputs.

在梯形图的某一横档上，当这个符号前面的路径上的其他指令都是“真”时，这个符号也将是“真”，“真”表示是物理意义上的“ON”。通常情况下我们把这个符号看作一个常开输出，该符号既可用于内部线圈也可用于外部输出。

OutBar / OutBar指令

The OutBar instruction is sometimes also called an OutNot instruction. Some vendors don't have this instruction. The OutBar instruction is like a normally closed relay coil. Its symbol looks like that shown below.

OutBar指令有时也称为OutNot指令。有些品牌的PLC没有这个说明。OutBar指令就像一个常闭的继电器线圈，它的符号如下所示：

An OUTBar (normally closed coil) symbol / OUTBar（常闭）符号

When there is a path of False instructions preceding this on the ladder rung, it will be True. When the instruction is True it is physically On. We can think of this instruction as a normally closed output. This instruction can be used for internal coils and external outputs. It is the exact opposite of the Out instruction.

在梯形图的某一横档上，当这个符号前面的路径上的其他指令都是“假”时，这个符号将是“真”，“真”表示是物理意义上的“ON”。通常情况下我们把这个符号看作一个常闭输出，该符号既可用于内部线圈也可用于外部输出。它与OUT指令完全相反。