APPARATUS FOR COMMUNICATION BETWEEN PERSONNEL INVOLVED IN FIRE-FIGHTING, RESCUE OPERATIONS, AND OTHER HAZARDOUS DUTIES-NAMELY, VOICE COMMUNICATION APPARATUS ESPECIALLY ADAPTED FOR USE BETWEEN WEARERS OF BREATHING APPARATUS; AND DISTRESS SIGNALING APPARATUS ADAPTED TO BE CARRIED BY HAZARDOUS DUTY PERSONNEL FOR SELECTIVELY SOUNDING AN AUDIBLE ALARM IN EMERGENCIES OR THE LIKE