Abstract: Apparatus for practicing throwing and catching baseballs having a pair of rectangular support frame members pivoted together along a common side. A wooden board having a coated surface is mounted on one of the support members. A baseball tossed against the coated surface of the wooden board is rebounded and caught by a user. A tubular adjustment mechanism permits the wooden board to be angularly adjusted so that the rebound trajectory may be changed as desired.

Abstract: A passband echo canceller achieves improved performance by providing a signal having a substantially uniform power spectral density to an adaptive echo canceller; the improved input signal is substantially uniform from approximately zero hertz to one half the operating or sample frequency of the echo canceller. This signal may comprise that range of frequencies occupied by the transmitted spectrum with added out of band noise.

Abstract: Unreacted ethylene contained in a gaseous light ends stream derived from a process for the production of ethyl acrylate from ethylene and acrylic acid utilizing a sulfuric acid catalyst, is recovered by intimately contacting, under controlled conditions of temperature and pressure, the light ends stream with the liquid sulfuric acid catalyst make-up stream which is passed to the ethyl acrylate process. Upon contact of the light ends stream with the sulfuric acid make-up stream, the ethylene reacts with sulfuric acid to form ethyl hydrogen sulfate and diethyl sulfate, both of which remain in solution in the sulfuric acid which is then passed to the ethyl acrylate process as a source of make-up sulfuric acid. Sulfur dioxide contained in the vent-gas stream is not absorbed into the sulfuric acid, and therefore not recycled to the ethyl acrylate process.