The full name of transistor is semiconductor transistor, which is a semiconductor device that controls current and is widely used in various circuits. It has three main working states, namely cut-off state, saturation state and amplification state.

1. Cut-off state: In this state, the base voltage of the transistor is lower than a certain threshold, resulting in no current flow between the collector and the emitter. When the transistor is in the cut-off state, it is equivalent to a short circuit and does not play an amplification role.

2. Amplification state: The base voltage of the transistor is higher than a certain threshold, resulting in sufficient current flow between the collector and the emitter. When the transistor is in the saturation state, it can provide the maximum current amplification factor, which is a common working state.

3. Saturation conduction state: The base voltage of the transistor is in the range between the cut-off state and the saturation state, resulting in the current between the collector and the emitter being proportional to the base current. When the transistor is in the amplification state, it can realize the signal amplification function and is often used in amplifiers and other circuits.

The working status of the transistor can be determined based on the potential of each electrode when the transistor is working. Therefore, during the maintenance process, electronic maintenance personnel often have to use a multimeter to measure the voltage of each pin of the transistor to determine the working condition and working status of the transistor.