Short answer : No

Dear DL,

If I understand what you're asking:

- the layout trackwork is seperated into electrically-isolated blocks

- there are seperate track busses for analog and DCC

- and each block has a "selector switch" which connects it to either the analog or the DCC track buss,
(and thus makes it either "analog controlled" or "DCC controlled" as required)

Does that cover the situation?

If yes, and the question is

"can I switch individual blocks between the 2 control systems during realtime operations?",

the answer is...
"...No, Don't Do That..."

While technically it's possible,
the risk of a loco or car-with-lights/similar "accidentally" crossing between a "Analog block" and a "DCC block",

and thus very-likely damaging one or both control systems,

 is waaaaaaay too high, and the resulting $$$ is not worth the risk.

There are no workarounds for this issue,
at least, not without adding serious levels of added complexity and cost which,

let's be honest,

could probably be better spent investing in decoders to make the full-blown switch to DCC (and avoiding the issue completely).

Of course, if $$$ is an issue, you could go the other way,
rip all decoders out of your existing DCC fleet, and migrate back to analog.
(It's the cheapest solution, at the risk of severely limiting many attractive capabilities of DCC)

If you must run a mix of analog and DCC locomotives via some "switchable control system",
I'd respectfully suggest you:

- avoid DCC-specific items such as automatic polarity-reversing units

- wire up all frog-switching and similar situations with turnout-throw-activated micro-switches or other Traction Control Agnostic solutions
(IE physically throw the turnout position, and the microswitch is triggered in consequence.
There is no need for physically eperate "turnout control" and "frog/block polarity" switch controls!)

- Wire up a single "track buss" that feeds all active trackage

- Equip your analog throttle with a quick-disconnect plug of some description

- Equip your DCC system with the same type of plug

- Equip the Track Buss with a matching socket

and literally plug-in the control system you want to use into the layout at the appropriate time.
(making sure that all locos of "the other type" are either parked on elevctrically-isolated-trackage, or removed from the layout at the time).

By doing this, you are powering the entire layout with a single common control system at any given moment,
(IE no risk of crossing over block-gaps/bondaries and frying "the other control system"),

and making your under-layout wiring a lot simpler.
 

Beyond a full-blown conversion one way or t'other,
(motor-only decoders can be had for under US$20,
and many "current era" locos are "plug n play" conversions),

the only other "mid-way" solution I can think of is to ensure that all of your DCC locos have "analog mode" capability and have it enabled. (Check your loco or decoder documentation).

This will allow your "DCC-equipped locos" to be operated on Analog track, but negates almost all of the benefits of DCC in the process. ("Analog Mode" is also know to be a source of "runaway train" behaviour when running on a DCC system with questionable wheel<> track contact. Most "committed DCC users" disable "Analog Mode" to eliminate "oddball" operation).

Happy Modelling,
Aim to Improve,
Prof Klyzlr

I have a simple layout and

I have a simple layout and can run either DC or DCC selectable with a DPDT switch.  Bring the bus feed wires out and connect them to the center terminals of the DPDT switch.  Connect DC power to one side and DCC power to the other side of the DPDT switch.  Now you can select which power type provides power to the bus. 

Have fun, Mark

That's be 2 votes for "No" then...

Dear Mark,

What you've described is essentially the same as above, only replacing the physical plug/socket with a 2-in/1-out switch

The critical element is still the same though, from where the control system "plugs in", the actual signal fed to the layout is the same throughout the layout. No risk of "adjacent blocks with different power sources" issues...

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Yes it can be done

But only if you either use a DC power supply to control the layout or switch it over to be totally DCC controlled. There is no in between. You should not run part of the layout on DC and part on DCC. Forget to switch one switch and your engine or power supply will let that magic smoke out. 

Bernd

It could be done, by why?

When I started building the new layout, DCC was new to me, so I thought "why not be able to operate it DC when I get the notion" . Long story short, once you use DCC, you will never go back to DC. DCC wiring is so simple.Brian

Yes, G1000vista

If I had been the first to say this, I would have been accused of bias. Since you said it, I'll just politely agree.

Seen it too many times to count.

vote 3

two power sources

and an on-off-on?  Is that how I'm reading that, frtizg?  Beats trying to do some sort of decoder rube-goldberg.

Switches on each module . . .

1/4" TRS connectors for power/buss applications?

Dear Fritz,

Some questions, if I may: 

1 - What happens if you have one "table" set for DCC,
another "table" set for analog,
and a loco runs accross/straddles the isolation gap between? Ever tried it?

(HINT: That was a rhetorical question,
I think Bruce already predicted the results of this "experiement" above... :-( ).

2 - Typical TRS 1/4" jacks only have 3 "terminals",

and for Paired analog + DCC track buss connections between "tables"/modules/sections,
logically you'd need 4 wires. (No valid "common" available between the two "busses").

How are you wiring the connectors?

or, have I mis-understood, (very likely, wouldn't be the first time ),
and the TRS 1/4" connectors are not actually used for module<> module buss connections?

3 - What happens if you inadvertently plug one of those TRS 1/4' Audio jack plugs not-all-the-way,
(for those of us in daily Pro Audio, we've done this more times than we care to admit...)

or a connector is re/moved while power/signal is applied?
(Hint: even Neutrik, Switchcraft, and Amphenol do not reccomend using TRS connectors for Power applications, as shorting the TRS segments is virtually inevitable during un/plug moves,
or if not fully pushed home. Personally, I prefer XLR for power connections ).

Happy Modelling,
Aim to Improve,
Prof Klyzlr

"Well it seemed like a good idea at the time....."

Ever heard that expression?  It would apply here..... while having a layout switchable between DCC and DC sounds good and may seem like a good idea...... it's not.  Sooner or later  you forget  which way the "selection switch" is thrown and "POOF"  something pays the price.

Michael

I actually did this,

and for what I think is a good reason.  My narrow gauge branch, which at this time (and for at least a couple more years) has no physical track connection with the standard gauge main, is wired through a DPDT/CO switch.  Then entire layout is DCC controlled, with a separate booster for the narrow gauge branch.  However, I have a large number of brass and die-cast narrow gauge locos that are not easily convertible to DCC, so I have the option to connect a DC power pack to the narrow gauge track bus to run analog locos for testing or breaking them in, or even operating the entire branch.  Since I'll be installing sound decoders into most of these, which will require significant mods to the running gear and wiring, that'll take a long time, both for the actual work, and for allocation of funds!  Hopefully, by the time I actually get the dual-gauge section installed I'll have converted some of these analog locos to DCC.  Meanwhile, I have the option to run either type.  While running analog, by the way, I don't have the DCC system energized so the DC signal doesn't ride on the digital signal.

Paul

Dear Paul, Understand the

Dear Paul,

Understand the logic, but the overriding principle still stands. The NG branch is either "all analog", or "all DCC" at any given time, it's not broken-up into individually-powered "blocks" or "sections" where a loco could potentially stray straight accross an iso gap, shorting both systems together.

How one wires up dual-gauge such that, with a "common rail",
the 2 systems don't interfer with each other, 
that's a whole 'nother game far in excess of the OP's question scope...

(Glad to hear it's working for you though!)

Happy Modelling,
Aim to Improve,
Prof Klyzlr

DC and DCC ? No problem for me.

I run both, but ONLY one at a time.  I have a small layout, my main line "loop" is about 60'.  This is not a club layout, not a big basement layout with 6 guys running trains, etc, etc,  this is my small layout, I run it, and it's only me in this house that runs trains.  I wired my latest layout with "blocks" like my last layout that used cab control, I separated both rails, ran a bus, 3 or 4 feeders on each block, and use my left over Atlas control switches to control it all.  DC is A  cab, and DCC is B cab.  Only one or the other is plugged in.  I will be replacing the old Atlas cab controls with the toggle switches, just because the Atlas controls are old, and I would feel better with a switch that gives a more "positive" feeling of each position.

You can get as technical as you want on this issue, and come up with all the theoretical situations, but if you have only one system running at a time, never both, you will have no problems.

My thoughts,

Mike.

DCC on a DC layout

Replace the DC throttle with a DCC system.  It works.  Done it a number of times.  The caveats about cross connecting need to be followed so physically disconnect ALL DC throttles and turn on ALL block switches to the DCC position.  Electrically, the block switches work the same as inline switches used for troubleshooting trackwork electrical problems.

Terry

Easy solution

Ahhhh, you guys are making this way too complicated!

dlwdan: Go out and buy yourself just one sound-equipped locomotive. Your interest in legacy DC won't last a week from the day it arrives, and then you can stop worrying. Better still: it'll be faster, cheaper, and more satisfying than doing all of that extra wiring that ultimately won't work anyway.

Jokes aside, there's no getting around the fact that the transition from DC to DCC is a jolting transition. Especially so if your existing locomotives predate the DCC-ready sockets. Hardwiring controllers isn't that difficult once you have the knack of it, but it's easy to destroy a locomotive or two while you're learning. At one point I was trying to heat some shrink wrap, and I found out the hard way that the shell plastic and the drive wheel spoke plastic will deform before the shrink wrap shrinks. Scratch one locomotive.

In 2004 or so I made the mistake of buying my first sound-equipped locomotive, and that was the start of a complete replacement cycle (because installing sound myself isn't something I want to mess with). Once your on DCC, moving to sound isn't so bad, because you can do it gradually. Even if you fall in love with having the sound, you can still use the mute locomotives as B units.

- shap

DC or DCC

If you are powering the entire layout with either DC or DCC then you could use a double throw double pole switch to select between your power sources. In this way you could run either DC trains or DCC trains but not both at the same time.  But your stationary decoders wont work, of course. I have used this system on my simple layout when I was converting to DCC. I would lay track and test using DC. Since then I have installed an OG-AR  as system power breaker and auto reversing a cross-over. so the DC power source is not an option any more because the auto reverser wont work with straight DC. ( I could run DC trains on a DCC layout using train #00 but was told it was not reccomended)

It can be done - But

Layouts have been wired for simultaneous DC and DCC operation, but it is not for the faint of hart for many of reasons stated in previous comments. For a look at a fairly complex layout that can simultaneously run DC and DCC check out the former and current layouts at the Tech Model Railroad Club of MIT ( http://tmrc.mit.edu). For a sense of what it can take to effectively implement a DC / DCC system check out some of the supporting circuitry from the old and new layouts at  http://tmrc.mit.edu/history/. Now this crew has had and continues to have access to substantial mental and physical resources, but even a simple system where DC and DCC actually coexists would not be a simple design.

Old TMRC Controller and PDP 11 Minicomputer (One of my favorite machines to play on.)

  New Control Circuit and controlling PC

Not very productive advice

Not very productive advice from the DCC guy.  I want to do the same thing.  I want to start with DC and I have a couple of good DC controllers that have never been used.

Wow, you just solved my issue

Wow, you just solved my issue on my layout. After all these years I'm finally going dcc, I just don't want to lose my dc block functions.

Thank you,

Bill