"The SB-83 may be off of an MSO. I didn't go and locate the NAVSHIPS 91822(B) but a note in the database says "Master/Slave Sync Controller For Mag Minsweeping"." KY-83 comes back as "Keyer Adapter KY-83()/S (Remote Control Tone Adapter Unit). MIL-K-16551 - BASE - SUPERSEDED" But I can't find any other references. KUrt