Introduction to PLC output types
PLC is an electronic device widely used in industrial automation, which can control various mechanical equipment and process flows. PLC output modules are used to control external loads such as motors, valves, indicator lights, etc. PLC output modules are generally of two types: transistor output (T output) and thyristor output (S output).

Transistor output (T output)
Transistor output modules use bipolar transistors (BJT) or metal oxide semiconductor field effect transistors (MOSFET) as switching elements.

Characteristics of transistor output:
1. Load voltage: Transistor output is suitable for low voltage loads, usually direct current (DC).
2. Load current: Transistor output is able to control smaller load currents.
3. Switching speed: Transistor output has a faster switching speed.
4. Power consumption: Transistor output consumes less power when turned on because it is equivalent to a switch.
5. Isolation: Transistor output generally has better isolation characteristics.
6. Control signal: Transistor output modules usually require a positive logic control signal.

Thyristor output (S output)
Thyristor output modules use thyristors (SCR) as switching elements.

Characteristics of thyristor output:
1. Load voltage: Thyristor output is suitable for high voltage loads, which can be alternating current (AC) or direct current (DC).
2. Load current: Thyristor output is able to control large load currents.
3. Switching speed: The switching speed of thyristor output is relatively slow.
4. Power consumption: Thyristor output has a certain power consumption when turned on because it has a conduction voltage drop.
5. Isolation: The isolation characteristics of thyristor output are not as good as transistor output.
6. Control signal: Thyristor output modules usually require a negative logic control signal.

Differences between transistor output and thyristor output
1. Load type: Transistor output is suitable for DC low voltage loads, and thyristor output is suitable for AC or DC high voltage loads.
2. Load capacity: Transistor output controls a smaller current, while thyristor output controls a larger current.
3. Switching speed: Transistor output has a faster switching speed, while thyristor output has a slower switching speed.
4. Power consumption: Transistor output has low power consumption when turned on, while thyristor output has a conduction voltage drop and power consumption.
5. Isolation characteristics: Transistor output generally has better isolation characteristics.
6. Control signal logic: Transistor output requires a positive logic control signal, while thyristor output requires a negative logic control signal.

Conclusion
The transistor output and thyristor output of PLC have their own characteristics and are suitable for different loads and application scenarios. Transistor output is suitable for low DC voltage, small current, fast switching, and occasions requiring good isolation. Thyristor output is suitable for AC or DC high voltage, large current, and occasions with low switching speed requirements.