Abstract: In a digital mobile system, to avoid distortions and fadings due to multiple propagation and the doppler shift, adaptive gain of the amplifier of a demodulator must be controlled with information derived from the signal at a high frequency. This is accomplished without the use of intermediate frequency selection filters by first demodulating the signal to base band, filtering out the desired signal and remodulating the desired signal to a higher frequency. From this remodulated signal the adjustable gain is controlled.

Abstract: A base station in a mobile digital system (TDMA/FDMA) utilizes a frequency hopping technique. The interconnection among receiver/transmitters (RT1-RTm) and process nodal points (NP1-NPm) takes place in base band using a common medium as distribution means of data relevant to the different users, which are entered on and sensed from at least one bus (B, B'). According to one embodiment two separate bus are foreseen, one for transmission and the other one for reception.

Abstract: A frequency discriminator designed to respond to a selected incoming tone frequency comprises a pulse generator connected via an adjustable frequency divider to a binary 8-stage counter which generates eight relatively staggered pulse trains whose cadence varies with the setting of the divider. This setting can be varied, e.g. in a programmed manner according to a pattern of tone frequencies to be recognized, while incoming signals are applied to an eight-path filter driven by the staggered pulse trains. When the cadence of the pulse trains matches an incoming tone frequency, the filter emits an output exceeding a predetermined threshold.