Abstract: Methods and apparatus for atmospheric sounding using acoustic chirps are disclosed, the transmitted and echo chirps being compared in a mixer that yields frequency sums and differences. Preferably, the mixing is performed as a complex multiplication in the Fourier domain. In one system (1) a signal generator (5) such as a PC sound card drives a loudspeaker (3) that serves as a transmitter and echo pulses are detedcted by a microphone (4) that serves as a receiver. Chirps transmitted by the loudspeaker (3) travel by different paths (7a and 7b) due to reflection from TILS or thermal inversion layers (2a and 2b) at different altitudes. The transmitted and echo chirp signals are compared in a mixer (6) from which various outputs (8 and 9) can be generated. One output (8) might be the magnitude of the difference between the transmitted and echo chirp tones, instant by instant, which is indicative of the altitudes of the respective TILs.

Abstract: Means for masquerading IP addresses for non-IP devices are disclosed, enabling non-IP devices or sub-networks having incompatible address spaces to be connected to an IP network and appear as addressable network objects. In one embodiment, the means may be a remote system controller (RSC) that has a block of IP addresses assigned to it for use with connected sub-networks or devices. Normally each assigned address will be associated with a management information base (MIB) containing data about the associated device, and each MIB will be associated with a protocol converter and I/O port connectable to the respective device or sub-network.

Abstract: Methods and apparatus for atmospheric sounding using acoustic chirps are disclosed, the transmitted and echo chirps being compared in a mixer that yields frequency sums and differences. Preferably, the mixing is performed as a complex multiplication in the Fourier domain. In one system (1) a signal generator (5) such as a PC sound card drives a loudspeaker (3) that serves as a transmitter and echo pulses are detedcted by a microphone (4) that serves as a receiver. Chirps transmitted by the loudspeaker (3) travel by different paths (7a and 7b) due to reflection from TILS or thermal inversion layers (2a and 2b) at different altitudes. The transmitted and echo chirp signals are compared in a mixer (6) from which various outputs (8 and 9) can be generated. One output (8) might be the magnitude of the difference between the transmitted and echo chirp tones, instant by instant, which is indicative of the altitudes of the respective TILs.

Abstract: A fading simulator for generating multipath-faded test signals which have attenuation notches of precisely controllable frequency position and attenuation depth from a modulated input signal of known bandwidth. The input signal is fed to a splitter that directs two in-phase components to a first path and a second path. The input to each path is divided by a splitter into in-phase and quadrature sub-signals having a quadrature phase relationship, each sub-signal being fed to a respective inverting attenuator, the outputs of the attenuators then being combined in a combiner and the combined output being passed through a variable delay line to generate the output of the respective path. The outputs of each path are then combined in a combiner circuit to generate the multipath-faded test signal. All four inverting attenuators are preferably substantially identical to one another so that the two paths have close to identical temperature-drift and other characteristics.

Abstract: The present invention provides a method and apparatus for evaluating the performance of a signal-processing device during a test period when an input signal is applied to the signal-processing device and an output signal is generated by it. A select profile of the input (or output) signal quality is derived at intervals in which the output (or input) signal lies within some predetermined range. The derived profile may be normalized with respect to the quality of the input (or output) signal throughout the test period. The profile is indicative of device performance of the device being tested. The method may be implemented in either hardware or software.

Abstract: A telecommunication system having a cellular mobile telephone system in which calls from cellular telephones are routed through a mobile service switching center exchange. Users of the system, having control of respective groups of mobile telephone are able via user terminals to access respective databases in a signalling processor and to place in the data base information about call parameters, such as call restrictions, for ones of the telephone of that user controlled group. When a call is made from any mobile telephone, the call signal is decoded at the relevant exchange and a determination is made as to whether the call originates from a mobile telephone which is a member of a controlled group. If so, the related database in the controller is accessed and the call is controlled in accordance with the appropriate call parameter, on the basis of the information in the related database.