Abstract: A carrier frequency communication transmission system has a premodulation band above the transmission position of the base primary group of 60-108 kHz and utilizes mechanical filters as channel filters and also a common group filter in order to filter out the primary group band. Bending resonators having longitudinal coupling are utilized as the mechanical filters. The frequency range of the premodulation band at its lower limit is determined by a frequency spacing of at least 4 kHz from the upper band limit of the primary group band and the upper limit of the frequency range is determined in that the interfering natural oscillations, inasmuch as they occur in the lower stop band of the channel filter, lie at least 12 kHz below the lower limit of the primary group band. Highly stabilized piezo ceramics is used as the electromechanical transducer material.

Abstract: A filter comprising a cascade arrangement of closed line CTD filtering loops has an intermediate CTD coupling loop formed with the adjoining output coupling of the preceding filter loop and input coupling of the succeeding filter loop. Disturbing self-oscillations outside the desired passband are eliminated by adjusting the voltage amplification factors of the amplifiers within the intermediate coupling loop, for example to from about five percent to about fifteen percent less than values selected to give a pure reactance branching circuit at the middle pass frequency. The resulting slight distortion of the transmission characteristic in the pass band of the filter can then be compensated by adjusting the amplifications of other amplifiers, and if necessary the capacitance conditions can be additionally altered.

Abstract: A switching circuit (2) consisting of CTD lines (p.sub.1,q.sub.1,p.sub.2,q.sub.2,p.sub.3,q.sub.3) is specified in which the properties characteristic for non-unidirectional microwave lines (FIG. 1) are also retained for CTD switching circuits (FIG. 2). To that end, CTD lines (for example, p.sub.1,q.sub.1) exhibiting mutually opposing conducting directions are combined into a line pair and each incoming line (p.sub.1) is connected with each out-going line (q.sub.1). The connection ensues partially via CTD lines (c.sub.1 +c.sub.1 ') and, for the other part, via a galvanic line (L.sub.1). Such switching circuits can be employed for the construction of CTD filters with steepness-increased transmission characteristic and also for the construction of correcting circuits.

Abstract: An electromechanical filter comprising a plurality of parallel mounted mechanical resonators which are generally cylindrical in shape with a plurality of input and output resonators operating in a bending mode and at least one intermediate mechanical resonator operating in a torsional mode and being generally dumbbell shaped with two or more cylindrical portions connected by a torsion member and with electrostrictive transducer input and output members connected to the input and output resonators so as to provide filters having wide band characteristics.