The 2904-12-300 part of Coto is a solid state relay. This is a type of relay that uses the power of semiconductor switches to control the switching operation of AC loads. This particular part features an operating voltage of 300 volts, a holding current of 4A, a switching power of 3 kW, and a switching time of less than 10 ms. It is designed for use in a range of sectors, including home automation, industrial, and commercial applications.