Understanding the different types of analog SWITCHES will help you understand how to connect signal lines!

For example, analog SWITCHES are primarily used when you want to insert SWITCHES into a circuit, such as for switching LEDs, POWER SUPPLIES supplies, audio signals on/off, or analog signals. Analog SWITCHES are connected in series with electrical signals or POWER SUPPLIES lines and can switch between ON and OFF. While SWITCHES have mechanical contacts, this explanation will focus on analog SWITCHES composed of semiconductor circuits.

Analog SWITCHES can have one or more inputs and outputs depending on their application. How do you want to use the signal line you're designing? Do you simply want to switch it ON/OFF, or use it for switching signal lines? The choice of analog SWITCHES and connection method will differ depending on the required specifications. Here are some examples.

• SPST (Single Pole Single Throw): It has one input (Pole) TERMINALS and one output (Throw) TERMINALS. The input and output can be switched ON/OFF, and are used, for example, to turn LEDs on and off or to switch POWER SUPPLIES ON/OFF.
• SPDT (Single Pole Double Throw): This type has one input (Pole) TERMINALS and two output (Throw) TERMINALS. One input TERMINALS is connected to either of the two output TERMINALS, and it is used, for example, to switch between audio and video signals or to select different POWER SUPPLIES.
• DPST (Double Pole Single Throw): It has two input (Pole) TERMINALS and one output (Throw) TERMINALS. It can simultaneously turn two independent circuits ON/OFF, and is used, for example, for simultaneously switching multiple POWER SUPPLIES or simultaneously switching multiple devices ON/OFF.
• DPDT (Double Pole Double Throw): It has two input (Pole) TERMINALS and two output (Throw) TERMINALS. Each input can be connected to two different outputs, and is used, for example, to switch the rotation direction of a motor or to switch between multiple signal paths.

For higher channel counts, configurations such as SP4T and SP8T are also available.

Furthermore, some devices have the same number of switching signals for multiple inputs. For example, the analog SWITCHES shown on the right side of the diagram has two switching signals for each of its two inputs. These are SPST SWITCHES x 2 (Dual SPST) and SPDT SWITCHES x 2 (Dual SPDT).

Figure: Symbol and internal configuration of an analog SWITCHES