Abstract: The invention relates to a transit modulator for jittering a signal (Uin) comprising a memory (3), a clock generator (2) connected to said memory (3) and generating a jitter free input clock (T) as well as a further clock generator (5) connected to said memory (3) and generating a jittered output clock (Tj). It is the object of the invention to provide a transit modulator which allows any kind of signals and thus also non-binary digital signals to be jittered. This object is accomplished according to the invention by a transit modulator in which an A/D converter (1) is pre-connected and a D/A converter (4) is post-connected to said memory (3).

Abstract: A process for measuring the phase jitter of a data signal using a phase demodulator. To perform an accurate and relatively simple measurement of phase jitter, the data signal is supplied to a phase comparator and an auxiliary clock signal derived from a predetermined clock signal is supplied to the phase comparator via a gate circuit and a frequency divider. If the phase difference between the two signals exceeds a predetermined value, a control circuit controls the gate circuit so that the phase of the auxiliary clock signal is modified until the phase difference drops below the predetermined value. The modified auxiliary clock signal is modified again, generating a comparison clock signal which is provided to a phase modulator having an integrator so that the edge of the corresponding pulse of the data signal falls in the middle of the ramp-like output signal of the integrator when the phase jitter is zero.

Abstract: The invention concerns a process for detecting the zero crossings of a data signal by employing of a comparator. To be able to accurately detect zero crossings even when the data signal is distorted due to transmission over a system with filtering characteristics, an auxiliary voltage corresponding to half the value of the difference between the measured maximum value of the data signal and the measured minimum value is generated. An additional voltage is formed by comparing a reference quantity that is proportional to the auxiliary voltage with the respective instantaneous value of the data signal and is added to the auxiliary voltage to form a total voltage. The total voltage is used to form the reference voltage of the comparator.