Abstract: A digitally controlled oscillator is provided with a memory, storing the half periods T.sub.i (i=1, 2, ..., n) of corresponding frequencies f.sub.i =1/(2T.sub.i) to be generated, and with a digital feedback circuit, in which circuit the half periods taken from memory are decreased by a fixed time value .tau. on a time sharing basis, and in which circuit, as soon as the residual values .DELTA..sub.i,1 =T.sub.i -k.sub.i,1 .tau.<.tau. are obtained, these residual values are increased by the corresponding half periods T.sub.i also on a time sharing basis, and each value so increased is repeatedly decreased by the fixed time .tau.. On repeating this process j times, the residual values can be expressed by: .DELTA..sub.i,j =T.sub.i +.DELTA..sub.i,j-1 -k.sub.i,j .tau., where each k.sub.i,j is so large that 0.ltoreq..DELTA..sub.i,j <.tau.. The digital feedback circuit is connected to n residual value counters, which are each supplied with a series of residual values .DELTA..sub.

Abstract: Disclosed is an automatic gain control (AGC) circuit for an IF amplifier utilized in the receiver of a pulsed radar. The AGC circuit is provided with a noise measuring circuit for determining the minimum value of a number of average noise levels over corresponding time intervals of given short duration within the length of time for the range-independent RF signal amplification in the pulse repetition period. Such a noise level, based on the minimum value, can be considered to be least influenced by rain clutter. The IF amplifier is adjusted to this noise level.

Abstract: A DC motor having a permanent magnet rotor and two Hall effect elements relatively displaced 90.degree. for switching the currents in the stator windings as a function of the rotor position. The stator includes at least two windings. An output transistor for each winding controls the current flow therein and the base currents thereof are supplied from a common source of constant current. First and second control transistors have their base electrodes connected to the output terminals of the Hall elements and their output electrodes coupled to the base electrodes of the output transistors. In any position of the rotor only one output transistor can conduct and each winding can be fully energized at most over an angle of 120.degree..