You don't need them.
As an analogue guy, you can switch turnouts by holding the blank ends of the wires together. Or switch by hand. Or use contact switches from the electronics supplier of your trust.
An a digital guy, you can install decoders that replace the control boxes.

Hear, hear!
I can do it with my finger without electronic control...

in my limited experience even with a digital layout you can use the control boxes you mention.
Using decoders or other digital amenities costs money compared to these cute little boxes.
Plus every decoder drains a bit of power from the control unit.
Depends on size of layout and money :-)

I use decoders and motors for C track turnouts. Expensive but good for routes etc with my CS3. For lights I just use a control box. Try a decoder in a turnout and I am sure you will like it.

You have said it, David... All this Analogue to Digital conversions of locomotives, solenoids, signals, etc. is going to cost me a bomb !! But, once it is done, I am sure I am going to like it. Thank you for saying so.

Cheers,
Ranjit

Still you don’t! You even use trafo or and power feeder.

Now, I am completely at a loss !! Do I use control boxes in a digital layout or don't I ? The answers to this very "stupid question" have become very large indeed.

Cheers,
Ranjit

Ranjit. Buy a turnout decoder and motor and fit it to a C track turnout. When you see what it does you will not want control boxes. Digital is expensive but it is worth going slowly and build up over time and buy the correct stuff. CS controllers work well with decoders and give you routes etc. Why buy manual switches in the digital age. Sometimes on here threads get out of control and do not give you what you want. My view is easy ... do not use control boxes and spend some extra cash to get the better option.

Ranjit, a lot depends on how you want to run your layout. If you are going to rely totally on automated route-control, or run from something like a CS2/CS3 then you may never need any control boxes.

But what about when you might want to run your layout on manual control?, ie actually just "play trains" ? Then, if you want to change turnouts (and signals) you either need to bring up the track diagram and use the stylus to change settings, (which personally I find too fiddly), or you have to be "hand of God" and reach over to switch the accessory manual - not really ideal unless the turnouts are right in front and in easy reach (but I still don't like to do that).

Personally, I prefer to wire in control-boxes so that I have the added flexibility. And I like the newer ones with the LED that show the status of the device. It's still being driven via Digital, but operated by hand (if that makes sense).

However, for me, I like it even a step further. I prefer a track diagram schematic control, using either the older 6041 Switchboard, or an equivalent. Then you can still choose whether you use push-buttons, or a wired-probe to 'touch' the setting as some people also like.

What I definitely would suggest is that even if you decide not to use control boxes, do keep open the option that you may change your mind in future, and make allowances for adding control boxes if you like. It's a minimal extra cost to install the wiring and leave it unconnected when you are actually doing the construction, than to try to add it later on.

Ranjit, unless Märklin has changed the underfloor mechanism and incorporating the thickness of your board they are not very reliable., there is so much play in them and with the K-track turnout mechanism it doesn't make it a secure operation., I got rid of all my underfloor motorized solenoids and exchanged it with proper servo motors, the benefit is, they are locked into a position and the linkage can't move hence the turnout mechanism can't move either but this again needs money and you have to have control boxes to operate the servo motors.
It is never a stupid question when it comes to outlaying a lot of money eventually and you could save a lot of money when asking questions before hand, it literally could save you thousands of dollars.

depending on the size of your layout, the amount of locos you're running at the same time, all of this has to be taken into consideration, whether or not you're able to run the locos single handed or you need an automated system., whether you can switch the turnouts and signals manually as Tom suggested., if not it will cost you money.
My main concern is is with Märklin signal or turnout products they are very expensive and there are alternatives at a much cheaper price and do the same job., whether you're talking about K 83's K 84's, signals, I've been in the fortunate position and made them myself with substantial savings.
It needs a lot of homework to establish what you need and at a later stage when you've got it all together (before purchasing anything) to share your plan with us and I would suggest not in bits and pieces but as a whole., one thing you also have to have in mind are you a handy person or would you rather put everything together products from a catalogue.
Being a Librarian you have to get into the habit of reading a lot about digital components and their use, asking questions about specific items can or could confuse you more than help you because each digital component has a link to another digital component and unless you know what you want and need the confusion can increase and for us to give you the right advice could be hampering your success.
You could finish up running around like a mouse on its wheel, getting enough exercise for your brain with ideas running wild but not much of getting a foothold to proceed with facts and figures, it took me 3 years to decide which command station to buy switching over from the Motorola system and it depends you may not need an expensive Märklin or ESU central station/command station and it may be enough to buy a second hand Motorala system, combine this with ESU decoders, you can expand it to 255 addresses and 12 Aux functions.
There are so many different options you can choose from, therefore read a lot beforehand and than put it all together.
It is already apparent with forum members giving you advice with different options and it seems you find it hard to analyze whats right for you therefore go back and read and read, some things you most probably will not find anywhere is the practical application of digital components as they can change options you have available to you as this topic has already shown
John

YouTube is a great source of information. Lots of how-to videos for beginners.
-And maybe you should read about DCC, and then YouTubers from UK and US really kicks in, and there´s a LOT of information available on the net!

Hi John... I will definitely look at the cost of Märklin digital components vs. other manufacturers and explore the "other options" when the time comes.

Cheers,
Ranjit

As pointed out, there is lots of information on using Radio Control servos as point motors. I believe the recent Marklin 60881 can control them, but I have not investigated this, so have no experience with setting them up.

The servos are available for good prices on eBay, so the cost of the Marklin point controller becomes the major cost.