If they want us to use transponders.. then they have to put up with the 1200
codes (or discrete glider code) all over their screens.

As Jim said... but not entirely accurate. And a response by another
responder, not entirely accurate.
Yes, if a "discrete" assigned code gets to close to another discrete or 1200
code, alarms go off.
If two 1200 codes get too close, alarms do not necessarily go off, 1200
(VFR) codes implies that the controller does not have the aircraft on the
radio frequency and there is nothing the controller could do about it.

"Most" fighter type aircraft can interrogate Mode 3 transponders on their
air to air search radars and get a return.
"Most" fighter type aircraft do not have TCAS. Modern Aircraft might.
"Transport" military aircraft may or may not have TCAS, it depends on their
vintage, and they do not have an air to air radar to "ping" a transponder.
" Heavy Bomber" military aircraft may not have TCAS, it depends on their
vintage, and they do not have an air to air radar to "ping" a transponder.

If a flight of 4 fighters (or more than one) is transitioning airspace
outside of a MOA, ATC will have the wingmen, "Strangle the parrot", so
everyone will only see one transponder return, not four and the ATC radar
will not "go crazy with alerts".

BT "retired military aviator" and one time ATC controller.

"JS" wrote in message
...
This morning's threads about transponders and collisions prompted...
During the trip to Joshua Approach which Cindy Brickner organised
last week, amongst other things we were presented with what happens at
the Air Traffic Control end when we are sending our location to them
via transponder.
If you are issued a discrete squawk code by ATC, and fly close to
another aircraft with a transponder; turned on and ALT encoding,
discrete or VFR (1200) code; then ATC computers start making noise
about the possible crash. They can only suppress so much of this
before the warnings sound like "something out of Star Wars".
Apparently two aircraft squawking VFR are visually reported as a
conflict but do not have the same level of alert.
Close to another aircraft could be:
On tow behind a transponder-equipped towplane.
Sharing a thermal.
Pair flying.
Not that gliders ever do any of that.
So as we're all moving toward using radios and transponders to keep
separation, be aware of the havoc we may be wreaking at ATC. Not a
good way to make friends! If you're Mode S, they have your
registration too!
As previously suspected, military aircraft do not use transponders,
so they get your position verbally from ATC but your current
transponder-based collision warning systems will do nothing.
Look out the window,
Jim