Transponder code 1000 vs differentiated 1234

Why do ATC sometimes give you 1000 and othertimes a differentiated code like 3456 for example ?thanks

Because the identification is done via the identifier that the Mode S transponder transmits to the radar stations. That’s also the reason why it is important to insert the correct flight identifier (=flight number, e.g. “DLH12KA”) in the FMS before each flight. Here in VATSIM all transponders are automatically Mode S capable and there is no need to insert your flight identifier in the FMS - except when you want to use PDC or CPDLC, then you have to do it.

I do not understand, I always use the same identifier AFR2257 and sometimes I get 1000 and other times a differentiated code like 1234

Not all ACCs are capable of mode S identification. This is simulated on VATSIM, so depending on where you fly and what ACCs your route leads through, you will either get 1000 or a discrete code.

Rather “not all ATC organizations within VATSIM want to be able to use Mode S identification”, although we have been doing it for the last 20+ years :stuck_out_tongue:

Ok thanks , looks a little strange !

It is not that strange, it is just that the discrete codes are the old system that worked with so called mode-c transponders, where planes were correlated to the flightplan by the controler observing e specific code being set by the aircrew. Later a new system called mode-s transponders was introduced where the signal from the transponder includes more details like the callsign, the mode-s identifier, the planes altitude and sometimes even speed and stuff.

Now in some areas of the world the controlers dont have or dont yet use the mode s-equipment in real life, so in those regions it is also not used on vatsim

The only FIRs where I have been given code 1000 are over Germany, and then only when transiting. When it’s not busy it’s quite common to get “squawk 1000” then direct to the other side of the FIR boundary.

Ok I understand

there are many other countries than germany which give you 1000, and not only for transit
for example yesterday I flew from LZIB to EHAM and was given 1000 at departure.

You normally get SQ1000 assigned before departure when you depart from an airport within the “1000-zone”, will stay in the 1000-zone and land at an airport within the 1000-zone. This is the most obvious case. E.g. when you fly from a Swiss airport to a German airport, you should get SQ1000 assigned. Flying from Germany to the UK ATC should assign a “discrete code” (anything else but SQ1000).

What countries are part of the 1000-zone?
IRL there is a thing called CCAMS - Centralized Code Assignment and Management System.
Guess what: a very dedicated member of VACC Switzerland has created a plugin for Euroscope (the radar app used by most ATCOs in Europe) that simulates CCAMS and it is called CCAMS as well!
If you click on the link above you’ll get to its GitHub-page and at the bottom you’ll find a list of countries that participate in the 1000-zone.
All airports starting with one of the following combination of letters are considered Mode S capable: EB,ED,EH,EL,EP,ET,LD,LF,LH,LI,LK,LO,LR,LSZR,LSZB,LSZG,LSGC,LSZH,LSGG,LZ, excluding EPCE,EPDA,EPDE,EPIR,EPKS,EPLK,EPLY,EPMB,EPMI,EPMM,EPOK,EPPR,EPPW,EPSN,EPTM

All clear now?

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Yes thanks for your explanations, my original question was to get better knowledege on this matter. And I got it thanks to you and the other guys who have answered to me.
But I wonder why a got a SQ 1000 flying from LZIB to EHAM, flying over Slovakia, Austria, Germany and finally the Netherland ?

if you look at the list posted by andreas just above you, italy (LI) is mode S capable, as well as Austria (LO), Germany (ED) and the netherlands (EH), Slovakia I would have to look up what the code is but probably also on the list, if you got squawk 1000.

edit: typo for italys code, thanks for spotting andreas

Just to be precise: “LZ” is Slovakia, you probably just mistyped by accident, but I wanted to make sure it is correct.

EDIT: I mistyped as well! You actually meant “LZ”, but that is Slovakia, not Italy. Patrick departed from LZIB, that is Bratislava.

As I said, all the coutries listed for my flight hereabove are mode S capable, so I should have received a SQ different from 1000 ?

No, as you seemed to have remained within the 1000-zone, you should have received SQ1000 for your flight.

No the other way around, mode S is the new system with more information that is not coupled to an individual code per plane, so everybody has squawk 1000 to signal the system to use the newer transmission protocol, the individual codes per plane were the old system (mode c)

Sorry guys for my bad and slow understanding !
Now I understand SQ 1000 is the new mode S system and individual SQ is the old mode C system.
Effectively I had understood the reversal.
Appologyze and thank you for the time you have spent to take me out of my ignorance status !!

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