How convenient in large rooms, to be able to turn on / off the lighting from any place convenient for you! And if there is a need to place 5, 10 or 20 switches?
Modern electrical equipment allows you to realize any of your fantasies. It all depends on the thickness of the wallet.
In one of the articles on this channel, I already talked about how to implement a similar circuit using pass-through and cross switches.
But in that scheme there was one big minus: a large cable consumption.
The circuit below is devoid of this shortcoming. Moreover, in the control circuit it is possible to use a cable with a small wire cross-section, because control current is small. (savings are obvious)
So, the main actuating element in this assembly is an impulse relay.
In order not to delve into the jungle of its principle of operation, I will say in simple words: when voltage is applied to the control contact for a short time, the relay turns on, and when voltage is applied again, it turns off.
What is the beauty of such a relay: applied voltage for a moment - turned it on, applied voltage again for a moment - turned it off.
As controls, buttons without fixing the position are used (these are used to turn on the apartment bell). The number of buttons connected in parallel is unlimited (at least 100, at least 1000!)
The only drawback is the high cost of the relay. But!!! If you calculate how much cable will go to a similar circuit with cross switches, then the relay circuit will be cheaper !