PB

PORTABLE TELEPHONES, DESK TELEPHONES AND PAGE TELEPHONES FOR USE IN MINE COMMUNICATION SYSTEMS

UNDERGROUND FIRE AND HEAT DETECTION SYSTEMS CONSISTING OF CENTRAL MONITOR AND CONTROL STATIONS, EXTENSION CABLES, HEAT SENSING CABLES AND/OR HEAT SENSING UNITS, LOCATION INDICATING UNITS, LINE MONITORING DEVICES, AND ELECTRONIC SIRENS AND MINE MONITORING SYSTEMS CONSISTING OF REMOTE TRANSMITTERS WHICH PRODUCE SIGNAL CHANGES IN RESPONSE TO CHANGES IN MONITORED CONDITIONS AND RECEIVERS FOR INDICATING THE STATUS OF MONITORED CONDITIONS