If you have already a layout, I advise that you let the operation of the switches and signals conventional. Further, you can upgrade in this way:

— Make an inventarisation of the locomotives that has already a decoder.
— You have to rebuild the older locomotives with a decoder. 66032 is really a nice one.
— Search on the internet for a second hand Delta Control. Then you can already start with 4 (and with a Delta Pilot 5) locomotives.
— If all locomotives has a decoder, upgrade your layout to Digital. Delta decoders will also work on Digital.
— Perhaps in a later stadium, you can upgrade the switches and signals also to Digital.

Note that conventional locomotives will not work on either Delta nor Digital. That is in my opinion the greatest problem. You firtst have to rebuild all locomotives with an decoder. What to do with a locomotive with a DC motor I don't know.

"Märklin Delta" is just a stripped-down version of the old "Märklin Digital" system. There is now also the new "Märklin Systems" which is only partly introduced so far.

Differences between the Delta and the old Digital system are:

Delta control unit can only control 5 different loco addresses, while Märklin Digital can control all 80 addresses. Control of other loco functions than speed and direction is also limited or absent with Delta control units. Delta control units can also not be expanded with add-ons like keybords (to control e.g. turnouts), memory, computer interface etc.

Delta loco decoders generally do not have regulated speed, which make them more load dependent and less smoothly running than the newer Märklin Digital decoders. Older Märklin Digital decoders are as bad as the Delta decoders in this respect. Delta decoders also generally have fewer function outputs (for e.g. light or telex couplers), or none at all. With many Delta decoders, the intensity of the head lights depend on loco speed, just like in analog mode. Delta decoders often also have fewer selectable addresses than Märklin Digital decoders.

Delta locos can be controlled with "Märklin Digital" and "Märklin Systems" control units.

"Märklin Digital" locos (and also the new "Märklin mfx" locos) can be controlled by Delta Control units, but functions like lights, sounds etc. might not work with Delta controllers.

The new "on-track-programmable" loco decoders (mainly "mfx" decoders but there are other on-track-programmable locos too) can not be programmed from Delta Control units, not what we know of in this forum at least.

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It isn't really the right time for investing in a transition to digital control right now. Both Delta and Märklin Digital are on their way out, and the new "Märklin Systems" units are only partly there yet. An alternative could be to go for the Intellibox from Uhlenbrock, but you could also wait and see until the "Märklin Systems" is really out on the market.

In the mean time you could get a Delta Control or a Märklin Systems Mobile Station just to get acquainted with digital control. Both Delta Control and Mobile station can be found really cheap. But both are insufficient in the long run.

More information on Delta:
Delta decoders have an internal 'dip switch' to set the address. There are 4 switches VS 8 for old Marklin decoders. This limits the address you can use for these Loks.
The Delta controller has a 4-position selector to select one of 4 predetermined addresses. If you have more than 4 Loks, you will need to change Lok addresses to avoid conflicts. (not fun)

However, the newer Delta controllers (66045) can be used as boosters to 6021 or IB (Intellibox). I have several I plan to use this way, so Delta is not totally useless.

Delta can be an easy entry to the digital world, as long as you know the limitations at the start. Realize that you will soon want more.

As for wiring, you can insert the Delta (Or IB) between the trafo and the layout. Use the Yellow and Brown to power the controller. (I use an old Blue analog trafo to power my IB test rig.)

Welcome to the 'Digital Black Hole". [}:)]

All the truth with few words.

The old Delta decoder with 4 switches can:
— Provide 4 addresses in combination with a Delta Controller.
For the 5th address you need to set a digital decoder to the address 80.
— Provide 16 addresses in combination with a Digital controller like 6021 and so on.

To boldy state that a Delta decoder with 4 switches can only set to 4 addresses is not true.

I think it's 15; the 16th setting is for analog. Not much difference though.
/Lars

I began digital operation with a Delta Control 4f.
You can turn lights on and off, but frustration begins if you buy a fx loco (in my case a BR152 with long distance headlights and whistle). Frustration grows if you have more than 5 locos and have to duplicate addresses.
With a PC and some freeware (using the Delta Control as a booster), you can address 255 locos with all their functions. This worked OK, but having to boot the PC to run a train was annoying.
So I finally bought an Intellibox.
In short: Delta Control cannot control functions f1 thru f4, is limited to 4 (5 with Delta Pilot, 15 with internal modifications) locos; Delta Decoders normally support 15 digital addresses (don't buy too many Delta locos!) and have no load regulation and neither minimum nor maximum speed can be adjusted.