Abstract: An analog-to-digital converting apparatus includes an analog controllable gain amplifier (A.sub.1) connected to an input of an analog-to-digital converter A/N. A gain control signal of the amplifier (A.sub.1) is obtained from at least one comparator (D16, D240, D224) for making a binary comparison between an output level of the analog-to-digital converter (A/N) and at least one predetermined threshold, and circuitry (SEL2, S.sub.2, I.sub.2) for controlling with respect to time the gain of the amplifier (A.sub.1) as a function of the result of the comparison.

Abstract: An image rejection mixer circuit comprises a pair of mixers (1, 2) to which are supplied input signals from an input terminal (9) and oscillation signals in mutual quadrature from an oscillator (11). The mixer output signals are combined in a combining means (19) to produce at its output (20, 21) a frequency-translated wanted signal free from frequency-translated image signals. The combining means comprises an acoustic surface wave filter and, in order to avoid the necessity of providing it with a pair of input transducers, with the consequent increase in the area of piezo-electric substrate that would entail, it is provided with a single input transducer of the four-phase or pseudo four-phase type.

Abstract: A symmetrical arrangement for forming a variable alternating-current resistance, which circuit arrangement comprises an elongate p,n junction or a ladder network of p,n junctions and resistors, the elongate p,n junction or the p,n junctions of the ladder network being connected between a source of control current and a source of bias current.