摘要:
A cellular telephone mobile unit position determining method which utilizes a plurality of range transceivers located at known fixed locations adapted to transmit approximately synchronized digital range signals. The method is especially adapted to determine the position of a cellular mobile unit within cellular service areas for determining billing charges and/or access restrictions. According to the invention, the fixed position range transceivers transmit range signals which are received by a mobile unit. The mobile unit determines either the time difference of arrival or absolute time of arrival of the range signals, which in turn is used to determine the mobile unit's position for cellular billing and/or access restriction purposes. The range transceivers are operable to receive an error signal and correspondingly adjust the output of the next transmitted range signal so as to drive the detected synchronization error to approximately zero.
摘要:
A position system and method utilizes a plurality of range transceivers located at known fixed locations and which are adapted to transmit approximately synchronized digital range signals for receipt by both a primary receiver and a supplemental receiver, the former disposed at a known location and the latter disposed at an unknown location. The range transceivers are adapted to transmit pulse sequences which include an error portion corresponding to the approximate synchronization error of each range signal. This error portion is constantly updated in accordance with the last determined synchronization errors of the corresponding range signals received by a secondary transceiver. In an alternative embodiment employing Code Division Multiple Access (CDMA) technology, the range transceiver time stamp on transmitted range signals may be adjusted to account for the measured timing error for a given range transceiver. The supplemental receiver receives the range signals and uses the same in accordance with known time of arrival or time difference of arrival calculation techniques to determine the position of the supplemental receiver.
摘要:
An audio-signal detecting device to be disposed in a user's earmuffs for protecting his eardrums against noise of high-decibel level is comprised of a receiving unit, a first audio-signal amplifying unit, a second audio-signal amplifying unit, a peak-detecting and inverting unit, a first amplifying unit, a peak-detecting unit, a first switch, a delay unit, a second amplifying unit, a second switch, a third switch, an adjusting unit, a third audio-signal amplifying unit, and an output unit. In keeping communicable with outside world, when a noise greater than a predetermined decibel level is detected, this device is supposed to attenuate or reject it temporarily, then, after an RC-constant time period, recover to communicate automatically.
摘要:
A system for marking a plurality of zones within a cellular service area. One or more marker transmitters are disposed throughout a cellular area to transmit a zone identification signal that is independent of normal RF cellular coverage to a mobile or portable cellular receiver. Each zone identification signal is transmitted in a radio frequency coverage area that illuminates the zone to be identified and is constrained by a similar transmitter jamming the zone signal. The marker transmitters are programmed to transmit the zone identification signal during a predefined time slot so that more than one marker transmitter may simultaneously transmit the zone identification signal, thereby increasing the area in which the zone identification signal can be received by the mobile unit. In order to reduce the area in which a zone identification signal may be received by a mobile unit, the marker transmitters may transmit a jamming signal at the same time as the zone identification signal is transmitted.