NMAC. RPTR ACFT DEPARTING UNDER ATC VECTORS SAW AN ACFT CLOSE AHEAD. THE OTHER ACFT TOOK EVASIVE ACTION ABOUT THE TIME THAT ATC ALERTED FLC TO TFC.

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OPERATING A SF340-A ACFT WITH THE TCASII DEFERRED. WE HAD JUST TAKEN OFF RWY 18L AND WE CLBED TO 400 FT AGL AND INITIATED A L TURN TO HDG 090 DEGS (TWR ASSIGNED). TWR THEN HANDED US OFF TO DEP CTL. I TOGGLED THE FREQ FROM THE STANDBY TO THE ACTIVE AND CONTINUED WITH THE CLB CHKLIST WHILE I WAS WAITING FOR A BREAK IN THE NET TO CHK IN. AFTER COMPLETING THE CHKLIST I WENT TO STOW THE CARD. (IT IS KEPT ON THE CTR OF THE GLARE SHIELD IN A POCKET). AS I WAS PUTTING THE CARD IN THE HOLDER I LOOKED THROUGH THE CAPT'S CTR WINDSHIELD AND I SAW A LIGHT CESSNA 150/152 TAN WITH BLUE AND MAROON STRIPES COMING TOWARDS US FROM THE FRONT L. THE CESSNA HAD APPARENTLY SEEN US AND INITIATED A R DIVING TURN AWAY FROM OUR ACFT. BY THE TIME I COULD REACT THE THREAT WAS GONE. AT THIS TIME DEP CTL BROKE IN AND SAID THAT THERE WAS POSSIBLE TFC AT 11 O'CLOCK. NOTHING FURTHER WAS SAID ABOUT THE TFC. THE CAPT ESTIMATED THE TFC TO BE 500 FT AWAY. WE VERIFIED OUR ALT WITH DEP AND CONTINUED. SOLUTIONS: DON'T DEFER THE TCASII EQUIP. MORE ATTN FROM US ON VISUAL SCAN. QUICKER ADVISORY FROM DEP (IF ACFT WAS IN CTL; IF IT WASN'T; IT WAS VIOLATING CLASS C AIRSPACE).