ZDC CTLR EXPERIENCED OPERROR AT FL200 BECAUSE OF LATE CORRECTIVE ACTIONS; I.E. FAILING TO REALIZE TRANSMITTER FUNCTIONALITY LIMITATION.

Narrative

SECTOR WAS BUSY WITH MULTIPLE RDU DEPS WBOUND; CLT DEPS EBOUND AND MULTIPLE ARRS TO BOTH GSO AND RDU FROM THE S. ALSO NUMEROUS ACFT OVERFLYING THE SECTOR BTWN 110 AND 150 PLUS THE BE9L AT FL200 ON A RTE (SBV-SAV) THAT CONFLICTED WITH ALL DEP AND ARR RTES. SUPVR WAS PLUGGED IN GIVING AN OVER THE SHOULDER CHK. BECAUSE OF THE JACK HE WAS IN I LOST FOOT PEDAL CAPABILITY. I BEGAN USING THE PTT BUTTON ON MY HEADSET. SHORTLY AFTER ACR X CROSSED MY BOUNDARY I ISSUED A DSCNT CLRNC SO I COULD GET HIM UNDER ACFT Y. NOTHING XMITTED. AFTER A FEW ATTEMPTS TO GET MY MIKE TO KEY UP I REALIZED THE PTT WAS DEAD. I THEN SWAPPED JACK POS WITH THE SUPVR AND REGAINED FOOT PEDAL CAPABILITY. I QUICKLY SWITCHED TWO ACFT AND THEN REISSUED THE DSCNT CLRNC TO ACFT X. ACFT X DID NOT START HIS DSCNT FOR 3 RADAR UPDATES AND THEN ONLY DSNDED 100 FT ON EACH OF THE NEXT 2 RADAR HITS. THE NEXT RADAR HIT CONFLICT ALERT ACTIVATED. ACFT WERE APPROX 8 MI APART HEAD ON. I EXPEDITED HIS DSCNT THROUGH FL190 AND CALLED TFC TO ACFT Y. BOTH PLTS SAW THE OTHER ACFT. MY HEADSET FAILURE CAUSING ME TO PLAY 'CATCH UP' DISTR ME FROM MY SCAN AND THE SLOW DSCNT CAUSED THIS ERROR TO BE UNAVOIDABLE. I ALSO DO NOT KNOW IF URET FLAGGED THIS SITUATION WHEN I ENTERED A LOWER ALT IN THE DATA BLOCK OF ACFT X. D-SIDE TRAINING WAS IN PROGRESS BUT THEY WERE ON A HDOF LINE.