Abstract: The invention relates to diacrylates and dimethacrylates having cyclic carbonate groups, and their use in dental materials.

Abstract: To convert an input-word sequence into a digital line code of half the bit rate of the input-word sequence, particularly for digital color television signal transmission, an encoder is disclosed which has a difference branch in which the difference (D.sub.i) between every two successive input words (X.sub.i-1, X.sub.i) is converted into a difference code word (D.sub.i) by adaptive PCM quantization, and a sum branch in which the sum (S.sub.i) of the same successive input words (X.sub.i-1, X.sub.i) is converted into a difference code word (S.sub.i +P.sub.i) in a hybrid DPCM encoder. These two words are combined into a line code word (C.sub.i) by an adder (9). The quantizing characteristic of the adaptive PCM quantizer (1) is selected as a function of the prediction error present within the hybrid DPCM encoder (2). The decoder at the receiver of the novel communication system splits up the received line code word (C.sub.i) into the difference code word (D.sub.i) and the sum code word (S.sub.i +P.sub.