More or less every camera has its own flash unit as a built-in part. But the built-in flash unit is obviously very small and also the flash light will not cover a long distance. In this case, additional heavy duty flash unit/s are very much required for the proper photography.
The automatic twilight lamp is a very simple and fully solid state device. Instead of an electromagnetic relay, TRIAC have been used to switch the lamp automatically. The Schmitt trigger stage using two transistors that provides flicker less ON and OFF operation of the lamp.