"24V DC Cooling Fan" electromagnetic relays (EMR) from the initial use of the telephone relay date, has been 150 years of history. With the development of the electronics industry, in particular the early 1970s breakthrough optical coupling technology, the solid-state relay (SSR, also known as electronic relay) have sprung up everywhere. Compared with the traditional relay, which has a long life, simple structure, light weight, reliable performance. "24V DC Cooling Fan" solid state relay no mechanical switches, and has such a high degree of compatibility with the microprocessor speed, important characteristics of impact resistance, vibration, low leakage, etc. Meanwhile, since this product is no mechanical contact, electromagnetic noise is not generated, so that no additional components such as resistors and capacitors to remain muted. The biography "24V DC Cooling Fan" relay system requires these additional components, therefore, the traditional relay often cumbersome and complex, and costly.