Nice link Hpasp

"Since the Shrike's introduction, the percentage of SAMs fired with radar guidance has been greatly reduced. The far greater number are fired in salvo and are unguided because the ground sites cannot afford to stay on the air. This has greatly reduced their effectiveness and has been a big boost to the morale of the strike pilots. It should surprise no one that an increase in SAM firings and an increase in Shrike firings occur at the same time. Most Shrike launches are the result of SAM activity and launch warnings."

I guess this is the SAM sites switching on the missile command transmitter, without launching a missile?