Abstract: Amplitude samples of voice signals to be transmitted by pulse-code modulation are compared with a quasi-exponential reference voltage generated during each sampling interval while a binary counter receives a train of isochronous clock pulses, the reading of the counter at the instant of a match being stored in a memory for subsequent insertion into a message frame. Positive and negative signals are distinguished by a sign bit preceding the amplitude code; in one embodiment the reference voltage is sequentially generated with opposite polarities in successive halves of a sampling interval, the counter having an additional stage to generate the sign bit. Decoding at the receiving end is achieved with the aid of another binary counter whose output is compared with the amplitude code and, in the event of a match, causes the instantaneous value of a similar reference voltage to be sampled and stored for subsequent integration.

Abstract: A ball universal joint for wave guides comprising a package of plates, each of which having therein a rectangular cross-section hole a quarter-wave length, the plates being compressed on one another by interposing balls separating and restraining the plates and being rotably carried in a rigid framework. Intermediate these plates, a rigid body is positioned and is fast with the framework and provides a curved intermediate step, in which a curved rectangular cross-section hole of average half-wave length is formed. The two end faces of the rigid body lie on planes forming a 90.degree. angle therebetween, so that the axes of the end plates in the plate package form a 90.degree. angle therebetween.