ARTCC WAS UNABLE TO CONTACT ACFT FOR A PERIOD OF TIME.

Narrative

DURING THE PERIOD IN QUESTION; 2-WAY RADIO COM (XMISSION AND RECEIPT) HAD BEEN NONEXISTENT FOR SEVERAL MINS. PRESENTLY; WE RECEIVED A SELCAL (4 TONE CHIME) FROM OUR COMPANY OPS CENTER; TOGETHER WITH A GRAPHIC TO CONTACT ATC ON THE FREQ TO WHICH WE WERE ALREADY TUNED. I PICKED UP THE MIC AND CONTACTED THE CENTER. THE CTLR TOLD ME HE HAD BEEN TRYING TO CONTACT ME FOR SEVERAL MINS (HAVING MADE 6 ATTEMPTS TO DO SO). I ASSURED HIM THAT WE HAD HEARD NOTHING. HE RESPONDED BY GIVING US A NEW FREQ TO CONTACT. WE SWITCHED OVER AND NOTHING FURTHER WAS DONE OR SAID RELATIVE TO THIS INCIDENT. PLEASE NOTE; HOWEVER; THAT THERE HAD BEEN ABSOLUTELY NO CONVERSATION BETWEEN THE COCKPIT CREW MEMBERS AT TIME OF THIS OCCURRENCE. ALSO; WHEN WE LOOKED AT IT THE MCP DISPLAYED 200 K; 10000' AND 000 DEGS. YET WE WERE TRAVELING APPROX 270 DEGS AT 39000' AND WERE NOT IN SPD INTERVENTION. THERE WERE NO FAULTS LISTED ON THE LOWER EICAS OR EITHER CDU. COULD AN EXTENDED PWR INTERRUPTION TO AVIONICS HAVE CAUSED THE SYS TO DEFAULT W/O EVER GIVING US ANY WARNINGS? WOULD THIS HAVE CAUSED AN INTERRUPTION IN OUR RADIO COMS?