Mode S
Hi,
why do you still have transponders on Boeing aircrafts where you can enter a 4-number code for Mode A (and C)? Isn't mode S the only mode used nowadays on commercial flights?
Also, how would a mode s tranponder work? Just switch it to standy before take-off, and then to "on" (just like with the A/C modes), but without doing/entering anything else? (since the ICAO 24 bit hex code would always be the same for a specific aircraft..)