PA28 INSTRUCTOR PLT AND STUDENT TOOK EVASIVE ACTION FROM CESSNA CITATION IN CID CLASS C AIRSPACE. THE TWR CTLR FREQUENTLY INSTRUCTS ACFT IN THE PATTERN TO SQUAWK STANDBY. THE INSTRUCTOR PLT ANTICIPATED THIS AND SQUAWKED STANDBY; THEREBY NEGATING TCASII IN THE CONFLICTING CITATION. THE ATCT LCL CTLR DID NOT ADVISE THERE WERE 2 CITATIONS IN THE PATTERN.

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I WAS 1 HR INTO A TOUCH-AND-GO BLOCK WITH A PRE-SOLO STUDENT. DURING DOWNWIND; WE WERE TOLD TO WATCH FOR A CITATION ON A 4 MI FINAL. PERHAPS 1 MIN LATER; I SAW A LOW WING ACFT ABOUT THE RIGHT SIZE ON A 1-2 MI FINAL. I CALLED TFC IN SIGHT; AND NOTED TO MY STUDENT THAT WE HAD EXCELLENT SEPARATION. WE TURNED BASE. WE REDUCED PWR TO 1500 RPM AND BEGAN TO DSND. A MOMENT LATER; TWR TOLD US THAT THE CITATION WAS ON OUR R (WE WERE IN L TFC). THE CITATION WAS SLIGHTLY BELOW US AND PERHAPS 2000 FT AWAY AT OUR 2 - 2:30 O'CLOCK POS. I IMMEDIATELY ADDED FULL PWR; AND INITIATED A CLBING R TURN TO AN E HDG. SHORTLY AFTERWARDS; THE CITATION CALLED US IN SIGHT. I ALWAYS TRY TO KEEP TRACK OF THE NUMBER OF ACFT IN THE PATTERN. THIS CAN BE DIFFICULT WHEN GIVING INSTRUCTION. THIS DAY; I LOST TRACK AND DID NOT REALIZE I WAS DEALING WITH 2 ACFT. I SUSPECT THAT THE CITATION WAS OUTSIDE 4 MI WHEN WE WERE GIVEN THE TFC CALL; AS IT WAS EASILY 2 MINS UNTIL WE INITIATED OUR BREAKOUT FROM 1 - 1 1/2 MI BASE. ALSO CONTRIBUTING WAS THE FACT THAT OUR XPONDER WAS ON STANDBY. OFTEN IN THE PATTERN AT CID WE ARE EITHER ASKED TO SQUAWK STANDBY OR ARE NEVER GIVEN A CODE. AFTER OUR BREAKOUT; THE CITATION ASKED TWR IF OUR XPONDER WAS ON; SO I SUSPECT THAT THE PLTS WERE FOCUSED ON THE TCASII FOR TFC AVOIDANCE. I SUSPECT THAT CALLING TO TFC IN SIGHT ON THE WRONG ACFT IS FAIRLY COMMON EVENT. AT 1 MI; MANY ACFT ARE VERY DIFFICULT TO DIFFERENTIATE IN THE BEST OF CONDITIONS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE INSTRUCTOR WENT TO DISCUSS THE 'SQUAWK STANDBY' PROB WITH THE TWR SUPVR. HE AGREED THAT STANDBY SHOULD NOT BE USED. LCL CTLRS WERE DOING THIS TO UNCLUTTER THEIR BRIGHT RADAR SCOPE. ONLY AFTER THE INCIDENT DID THEY REALIZE THAT THEY WOULD NOT ISSUE THE SQUAWK STANDBY INSTRUCTION. ACFT VFR IN THE PATTERN ARE NOW TO SQUAWK 1200.