Abstract: A circuit arrangement for reproducing in an output circuit (4) a current (i1) flowing in an input circuit (1) comprises a PNP-current mirror (2) to the input (2-1) of which the input circuit (1) is connected. The mirror output (2--2) is connected to the emitter of an output transistor (3) of the PNP-type the collector of which is connected to the output circuit (4). The base of the transistor (3) is connected to the input (5-1) of an NPN-current mirror (5), whose output (5-2) is connected to the input (2-1) of the PNP-current mirror (2), so that the effect of the base current (ib) of the transistor on its collector current will be compensated for.

Abstract: An adaptive delta modulator must produce at its output a periodic 0-1 sequence when the input signal (w) to be coded assumes zero value. The delta modulator of the present invention is provided with a generator (GE) to produce a periodic 0-1 sequence which is transmitted to the receiver instead of the delta coded signal when the input signal to be coded assumes zero value. This generator (GE) is switched to the output line of the delta modulator at the instant at which the output voltage (Us) of a filter (IN) in the feedback path of the delta modulator, for determining the instantaneous quantizing unit of the delta modulator, assumes zero value. If this filter (IN) is implemented with digital components, the generator (GE) is triggered by the output pulses of a gate (G1) whose inputs are connected to the respective locations of the input signal storing means of the filter (IN). A delay line (V) prevents triggering of the generator (GE) at extremely short pauses in the input signal (w) to be coded.