Abstract: This invention relates to a convolutional encoder which encodes original data into convolutional codes by using a multinomial from which predetermined terms of the generation multinomial for generating the original convolutional codes are eliminated to thereby achieve high transmission efficiency as well as high error correcting capacity. The maximum likelihood decoder which is provided on the receiver side to correspond to the encoder can decode in maximum likelihood by calculating the branch metrics of received encoded data and decode the original data in correspondence to the coding rate of the original data with those branch metrics.

Abstract: A cross-correlated baseband signal processor for providing in-phase and quadrature phase shifted NRZ signals from an input signal, apparatus for cross-correlating the in-phase and quadrature shifted signals, and apparatus for generating in-phase and quadrature shifted intersymbol-interference and jitter free (IJF) modulated output signals having amplitudes such that the vector sum of the output signals is approximately the same at virtually all phase angles of each bit period. The resultant cross-correlated bandlimited PSK signal (XPSK) has an almost constant envelope and thus it can be passed through a saturated amplifier without AM/PM and AM/AM degradation and without the need for post-amplification filtering, as there is no spectral restoration (regrowth).

Abstract: A membrane type keyboard associated with a data terminal device is disclosed which is sealed to prevent the introduction into the interior elements of the keyboard of water or other types of liquid contaminants encountered during the operation of the terminal device. The keyboard includes an outer frame member which forms an air chamber extending around the perimeter of a raised keyboard, thereby preventing any liquid spilled on the keyboard from reaching the interior elements of the keyboard. The frame member is easily removable from the keyboard, allowing the interior elements to be replaced or exchanged in accordance with the business environment in which the terminal device is to be used.

Abstract: Aluminum carbonate hydroxide ammonium, a new compound, is produced by causing a solution of ammonium hydrogencarbonate to be reacted upon by a soluble aluminum salt. .alpha.-Alumina is obtained by thermal decomposition of this ammonium aluminum carbonate hydroxide. By sintering said .alpha.-alumina, there is obtained sintered .alpha.-alumina.