ICT（In-Circuit Test），An automatic testing system for assembling circuit boards, also known as an online static testing equipment for circuit boards, is mainly used for testing assembled circuit boards (PCBA). The term 'online' here is a literal translation of 'In Circuit', mainly referring to components being online. Online testing is a testing technique that continuously opens circuits without removing component pins. "Online" reflects the emphasis of ICT on detecting assembly issues of circuit boards through testing of components or open/short circuit states on the circuit.

The basic functions of ICT can be used to measure the open and short circuits, resistance, capacitance, inductance, diodes, IC protection diode testing, etc. of circuit boards. According to statistical data from the circuit board assembly industry, assembly defects are mainly reflected in welding open circuits, short circuits, offsets, missing parts, etc., accounting for more than 90%. Therefore, the principle of online testing technology application is to quickly detect faulty components or assembly defects, and accurately locate and classify defects.

ICT can be regarded as an automated advanced multimeter, and due to its circuit isolation (Guarding) function, it can accurately measure the actual value of each component in the circuit.