Abstract: A wireless telecommunication system for an equipment in an underground structure is disclosed. The system comprises a metal cover fitting in an opening of the underground structure while being supported by a shoulder. A porthole is formed in the cover. The porthole has a lens in plastic material letting radio waves pass. A cradle hangs across the opening. An antenna arrangement is mounted on the cradle and extends near and in alignment with the lens. A radio transceiver connects to the antenna arrangement and to the equipment in the underground structure to establish a wireless telecommunication with the equipment via the antenna arrangement and the lens.

Abstract: A wireless telecommunication system for an equipment in an underground structure is disclosed. The system comprises a metal cover fitting in an opening of the underground structure while being supported by a shoulder. A porthole is formed in the cover. The porthole has a lens in plastic material letting radio waves pass. A cradle hangs across the opening. An antenna arrangement is mounted on the cradle and extends near and in alignment with the lens. A radio transceiver connects to the antenna arrangement and to the equipment in the underground structure to establish a wireless telecommunication with the equipment via the antenna arrangement and the lens.

Abstract: A method and apparatus for operating two switches connecting respectively a load to power source terminals in response to a switch control signal. The invention detects a signal indicative of current direction through the load to identify one of the switches as an active switch. If the switch control signal is for opening the active switch, an opening gate signal is sent to the active switch and a predetermined time period is triggered. If the switch control signal is for closing the active switch, an opening gate signal is sent to the other switch, a predetermined time period is triggered, and a closing gate signal is sent to the active switch when the predetermined time period of the timer associated with the other switch has elapsed.