AN EMB120 DELAYS ITS DSCNT WHEN THE PF FAILS TO HEAR CLRNC. PNF DID; REPLIED TO CALL; THEN WENT OFF TO COMPANY RADIO AFTER SETTING ALT ALERTER.

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I WAS FLYING AS PNF AND TOLD THE FO THAT I WILL CALL THE COMPANY TO NOTIFY OUR ARR. WHILE I WAS TRYING TO CONTACT THE COMPANY; ATC INSTRUCTED US TO DSND TO 6000 FT. I HEARD THAT AND I ARMED THE ALT ALERTER AT 6000 FT. AFTER THAT; WE DISCUSSED THAT THE STATION USUALLY DOES NOT ANSWER THE COMPANY RADIO CALL; ALSO MY HEADSET AUDIO WAS INTERMITTENT AND WHILE I WAS CHKING INTERCOM WITH THE FO; ATC WAS CALLING US BUT WE DID NOT HEAR FIRST TIME. FINALLY WE HEARD ATC CLRING US TO LOWER ALT (PROBABLY 3200 FT). AT THAT TIME THE FO NOTICED THAT ALT ALERTER IS ARMED AT 6000 FT AND WE DID NOT DSND FROM PRESENT 11000 FT. I SHOULD HAVE NOT TOUCHED THE ALT ALERTER WHILE I WAS CONTACTING THE COMPANY AS IT IS THEN THE FO'S JOB. THEN ATC WOULD HAVE CALLED HIM REPEATEDLY IF HE DID NOT HEAR THE CALL AT THE FIRST TIME. INSTEAD I DIALED THE ALT ALERTER WHICH HE MISSED TOGETHER WITH ATC CALL. AFTER COMING BACK TO PNF DUTY AFTER FUTILE COMPANY CALL; I WAS FURTHER DISTR BY THE HEADSET/INTERCOM PROB AND MISSED THE FO'S FAILURE TO START DSCNT AS INSTRUCTED; RESULTING IN POSSIBLE ATC ALT VIOLATION. THIS IS THE REASON WHY CRM COM PROC MUST BE STRICTLY FOLLOWED.