Abstract: A network for a mine or other hazardous environment is provided. The network can include a plurality of access points that can communicate with each other. The access points can be deployed along a plurality of pillars in a room-and-pillar mine. The access points can interconnect a mobile wireless client device within the mine with an operations centre. In the event of an explosion or other disaster, a UPS battery back-up and the redundancy of the access points can increase the likelihood that a link between the wireless client device and the operations center can be maintained.

Abstract: A network for a mine or other hazardous environment is provided. The network can include a plurality of access points that can communicate with each other. The access points can be deployed along a plurality of pillars in a room-and-pillar mine. The access points can interconnect a mobile wireless client device within the mine with an operations centre. In the event of an explosion or other disaster, a UPS battery back-up and the redundancy of the access points can increase the likelihood that a link between the wireless client device and the operations center can be maintained.

Abstract: A door operator provides enhanced security for controlled vehicle access by employing transmitters having unique identity codes that are fixed in manufacture. A receiver includes a nonvolatile read/write identity code memory for storing the authorized identity codes. If a received identity code is found within this memory, then the user is authorized and the door is opened. Otherwise, the user is not authorized and entry is refused. A remotely disposed memory controller controls the authorized identity codes stored in the identity code memory, which is preferably electrically erasable programmable read only memory (EEPROM). The memory controller is preferably a desk top computer including a data base program with the identity of authorized users. The identity code of transmitter held by a formerly authorized used can be determined via the data base program and deleted from the identity code memory without requiring return of the transmitter.