What was found
AFTER DEPARTURE FROM MHT, THE PILOT ATTEMPTED ROUTINE RADIO COMMUNICATIONS. WHEN THE PUSH-TO-TALK SWITCH WAS RELEASED IT REMAINED STUCK IN THE DEPRESSED POSITION RESULTING IN AN OPEN MICROPHONE. THE PILOT SWITCHED TO AN UNUSED FREQUENCY TO UNBLOCK MHT COMMUNICATIONS AND ESTABLISHED CELL PHONE CONTACT WITH MHT. THE PILOT WAS CLEARED TO RETURN TO MHT AND LANDED. NO EMERGENCY WAS DECLARED. THE SWITCH WAS REPLACED, AND THE AIRCRAFT RETURNED TO SERVICE.