The ways of a switch are the positions it moves to not counting off, so a flick switch with centre off is not considered as three way only two way, you can get three way switches, but not seen any flick switches three way, mostly they are rotatory switches, I have one on my oven to select which elements are used, I think 12 way from memory.
So standard two way switching named after the switches it uses is
but in school we were taught
both work, but the former means no connectors in the switch. This can be extended
to include a change over switch, also called reversing switch or intermediate switch. Some dimmers have the switch and dimmer with independent contacts so in the first diagram the right hand switch could be a dimmer.
However you should not dim halogen lamps as it causes them to go black and reduces their life, and compact fluorescent is rare to find one which can be dimmed, so the dimmer switch went out of popularity and we started splitting the lighting, either wall and central, or central split 1/3 and 2/3 which gives three levels of lighting with two switches.
With the LED bulb dimming is possible again, and the EU law said the package needed to say if the bulb was not dim-able, but it did not say the manufacturer had to stipulate how it could be dimmed. There are two things included with most LED packages, one is a leak resistor, AC can pass with capacitor and inductive linking so it is possible the wire to switch can act as a capacitor and send some power to light even when switches off, the resistor is bulb leaks this away, but dimming switches with no neutral add to this small current and if can build up and cause some bulbs to flash when switches off. The second is the bulbs when switches on can shimmer this is stopped by using a capacitor inside the bulb, but no information is given to size of leak off resistor or capacitor size, so some times it can result in flashing or a shimmer.
Also all this results in LED bulbs not being as efficient as they could be, some are only 75 lumen per watt, but some smart bulbs can be up to 100 lumen per watt, so in general there has been a move away from dimming switches and using smart bulbs instead, specially since you can also set the colour temperature or even the colour.
But the smart bulbs are also a mine field, some of mine are Zigbee and need a hub, some connect direct to wifi, and with mine all use same app on phone called smartlife. With zigbee they can be linked to a remote control and I have a set of bulbs in wife's bedroom worked by a zigbee remote one a wall light the other a table lamp. Her ceiling lights are G9 and not found smart G9 bulbs so that still uses an energenie smart wall switch, I had 5 of those switches, now down to 2 as they failed. And when they failed it was a pain finding a standard switch and turning off all lighting power to change the switch, far easier if a bulb goes wrong, I can swap without turning off all the lights, same with smart sockets.
As yet cross fingers no smart bulb has failed, but a year ago would have said that for smart switches as well.
The Lidi remote control comes with a back so can be screwed to the wall if required just like a standard switch, but held with a magnet so can be also removed when you want, I prefer remote controls to using phone, the Lidi remote was simple,
but only sold with GU10 lamp unit and three GU10 lamps, you can get a more complex remote
but gets more costly, I have these
remotes with energenie 4 independent controls and I tried to get one for rest of zigbee
but simply can't get it to work, and this is my problem I don't walk around at home with mobile phone in my pocket, when I get home it goes on charge, so prefer a remote control as side of bed or on coffee table to turn lights on/off.
The main light in living room has 8 bulbs, so that would be rather expensive to use smart bulbs in, I have a new fitting for top of stairs with a smart relay in it, once fitted I will say how it works, but as yet still in the box, theory is two way switches converted to extra low voltage and the 5 GU10 bulbs split to centre and 4 around outside with centre being colour changing so we can have 1, 4 or 5 bulbs lit, and can switch with phone or wall switch. But not fitted yet. Need a ladder to do the job.
