Sorry, its another one of my random ponderings on operational ATC

What is the system with what transponder code your given?

The two cases i'm interested in are either an IFR flight, how is your code generated? And if your transisting a persons airspace do they have a set number of codes to use. eg 3100 - 3200? I've noticed if i'm pottering about VFR and go through an airspace I might be given 3250, and the next person would be given 3251

in Australia the codes are randomly generated by our system.

<<if i'm pottering about VFR and go through an airspace I might be given 3250, and the next person would be given 3251>>

Is that not logical? ATC Units dealing with random traffic usually have a block of codes and they use them in turn. There are various codes set aside for specific purposes too.

In Controlled Airspace, codes are usually allocated depending on the route or destination and will often be allocated by a computer which also links the code to the aircraft callsign to enable that to be displayed on the radar.

HTH

A little more insight here:

ORCAM (http://www.eurocontrol.int/airspace/public/standard_page/172_ICAO_ORCAM_Users_Group.html)

List of UK SSR Codes here (http://www.nats-uk.ead-it.com/aip/current/enr/EG_ENR_1_6_en.pdf)

Yes, units will have codes that they can assign to transit aircraft or non-airways arrivals and departures. This will mean that other radar units can see if you're working an aircraft that they can see.

Although I would be suprised if you were iven 3250 / 1 as though acceptable to the FDP would not be the best use of Superdomestic codes.