A COMMUTER FLC READ BACK A CLRNC FOR PLT'S DISCRETION TO A LOWER ALT; BUT THE CLRNC WAS FOR ANOTHER ACFT. WHEN THE DSCNT WAS BEGUN; THE ARTCC RADAR CTLR INTERVENED. ALTDEV ALT EXCURSION.

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WE WERE CHKING THE ASOS AT OUR DEST; FCA; AND RECEIVED A CLRNC FROM ZSE TO 'DSND AT PLT'S DISCRETION TO 9000 FT.' AFTER CHKING THE ASOS; I CALLED OUT OF 17000 FT. WE WERE THEN INSTRUCTED TO CONTACT ZLC. ON INITIAL CONTACT I RPTED AT 14000 FT DSNDING 9000 FT. SALT LAKE SAID 'WHERE DID YOU GET THE 9000 FT?' I REPLIED; 'FROM ZSE.' WE IMMEDIATELY LEVELED OFF AND THERE WAS A PAUSE WHERE APPARENTLY SALT LAKE WAS CHKING WITH SEATTLE. SALT LAKE CAME BACK AND SAID THAT THE CLRNC WAS FOR ANOTHER ACFT. WE QUESTIONED THIS DUE TO THE FACT WE HAD READ IT BACK; AND ASKED IF THERE WAS A PROB; AND SALT LAKE SAID 'NO THERE IS NOT A PROB; YOU ARE OVER LOWER TERRAIN NOW; DSND AND MAINTAIN 9000 FT.' THE MINIMUM OBSTRUCTION CLRNC ALT ON THE AIRWAY IS 9600 FT; AND WE NEVER WENT BELOW 13400 FT BEFORE BEING RECLRED BY SALT LAKE. APPARENTLY THERE WERE NO CONFLICTS. AFTER REVIEWING THIS EVENT IN THE COCKPIT; WE STILL BELIEVE WE WERE CLRED TO 9000 FT BY ZSE. AT THIS POINT ON THE AIRWAY; IT IS ROUTINE TO RECEIVE A LOWER CLRNC; UNLESS THERE IS A CONFLICT WITH LOWER TFC. THERE WAS NO TFC CONFLICT. WE WOULD HAVE TO HEAR THE TAPE TO BE CONVINCED THAT WE RESPONDED TO SOMEONE'S CLRNC. IT IS COMMON FOR CTLRS TO WORK MULTIPLE SECTORS HOWEVER; AND NOT BEING ABLE TO HEAR ACFT IN THOSE OTHER SECTORS DEFINITELY SETS UP A SIT RIPE FOR CONFUSION. SUPPLEMENTAL INFO FROM ACN 326838: THE FO ACKNOWLEDGED THE CALL; REPEATED IT COMPLETELY WITH OUR CALL SIGN.