NPN stands for Negative-Positive-Negative. It is a type of bipolar junction transistor (BJT) configuration where the middle layer is made of p-type semiconductor material sandwiched between two n-type semiconductor layers. This configuration allows for the amplification of electrical signals in electronic devices. In the telecom industry, NPN transistors are commonly used in amplifiers, oscillators, and signal processing circuits to boost and control the flow of signals in communication systems. The NPN configuration offers high gain and fast switching speeds, making it ideal for applications requiring precise signal amplification and modulation.