How does the flash flash?

There are basically two ways to flash. One is to use an external wireless signal transmitter, which is installed on the hot shoe of the camera or the line interface of the flash, and the receiver is installed under the hot shoe seat of the flash, and then the same communication channel is set, so that the flash can be controlled in this wireless way when the camera presses the shutter, which is widely used in studio photography. The other way is to turn on the active mode (master) when connecting the camera through the active or passive control mode set by the advanced flash, and then set several other flashes as slave, that is, passive mode, so as to realize the wireless flashing of the passive flash controlled by the master flash under the condition that the signals of the signal receiving ends of other flashes and the signals of the active flash are not shielded.