The indicator LED driver circuit that is supposed to turn on a LED for the 5V signal line on active LOW logic level. The LED is powered from higher voltage than logic level at input like 10V/12V. LED current limiter resistor value should be adjusted to the specification of the actual LED.
Real life implementation is powered from 10V and use separate N-channel logic level MOSFET, particularly 2N7002.
To minimize the physical circuit size, use dual SMD MOSFETs (2N7002DW, BSS138AKS, SSM6N37FU and similar) and 0402 size resistors.
