A time interval (delta t) is defined which is the interval between levels of first and second logical variables (NHW, PHW) for consecutive half-waves of the mains voltage (U Netz) or current (I Netz). A capacitor (C) is charged during the time interval and the value of stored energy compared with a reference value (Uref). The contents of first and second flip-flops (FF1, FF2) are set to "zero" when the reference value is reached. The contents of the first flip-flop is set to "one" on a first level charge of the first logical variable (NHW). This level charge prevents setting of new contents for the second flip-flop. The pulse sequence on the output of the first flip-flop represents the system clock (C1). ADVANTAGE - System clock has high security against mains interferences powerful enough to cause change of voltage polarity within a half-wave of mains voltage.

Producing mains-driven clock pulses - setting contents of two flip=flops set to zero when capacitor is charged to reference value

This circuit arrangement is needed when the clock in standard frequency systems is to be conditioned in such a manner that digital chips can be driven. At the same time, the alternating current signal is to be monitored. It is proposed to use a standard or HCMOS Schmitt trigger for converting an alternating-current signal into a square wave signal of the correct frequency and to combine the latter logically with a signal of another Schmitt trigger which, at the same time, is used for monitoring. Standard frequency systems.

Circuit arrangement for converting an alternating-current signal into a binary signal

of EP0372646To stabilise the frequency emitted by a crystal oscillator, a first crystal of a crystal oscillator is operated at the turn-over point of its temperature/frequency characteristic and kept at constant temperature in a thermostatic housing. The thermostatic housing contains a second temperature-dependent crystal of an auxiliary oscillator which regulates the heating of the thermostatic housing. It is proposed that the thermostatic housing is constructed to be symmetrical and exhibits two chambers for accommodating the crystals of the crystal oscillator and of the auxiliary oscillator, the frequency of the auxiliary oscillator corresponding to the frequency of the crystal oscillator. The crystals of the crystal oscillator and of the auxiliary oscillator are provided with crystal housings which are in each case identical. Clock supply devices for communications engineering.

Schemmel Hans-Robert

Papers

Circuit arrangement for converting an alternating-current signal into a binary signal

Quartz oscillator arrangement

Anordnung fuer einen quarzoszillator