Abstract: Disclosed are compounds of the formula: X Y Z A P Q T which are highly potent, selective factor IIa inhibitors, X, when present, may be connected to T, may be H, CH.sub.3, an acyl group, or a general protective group. Y is D-DPA, D-Phe, D-Val, D-Ile, D-Nle, a phenylsulfonyl, Dansyle, or 8-(1,2,3,4-tetrahydroquinolinosulfonyl) compound. Z, when present, is Gly, L/D-Pro, L/D-Ala, L/D-Leu, aminoisobutyric acid, a substituted or unsubstituted L/D-Pro ring homologue, or L/D-Val. A may be (I) wherein M is --CO--CF.sub.2 --(CO).sub.s --, --(CO).sub.d --NH--, --(CO).sub.d --(CH.sub.2).sub.p --, or --CH(OH)--(CH.sub.2).sub.p --, d is 0-2, p and q are 0-5, and s is 0 or 1, or A is a proline-like group. P and Q (if Q is present) are substituted or unsubstituted amino acids selected from the group consisting of L/D-Phe, L/D-Cha, L/D-Nal(1), L/D-Nal(2), L/D-phenylglycinyl, L/D-Leu, L/D-Ile, L/D-Nle, L/D-Arg, L/D-Lys, or L/D-His. T may be connected to X, or may be --OH, --OR.sup.4, --NH.sub.2, --NHR.sup.4, or --NR.sup.4 R.

Abstract: Adaptive extrema encoding reduces chipping noise by reducing the added-noise signal for low level input signals. Alternatively, the input signal is controlled.

Abstract: An extrema coding circuit comprising a differentiator and a noisy limiting-amplifier. The limiting-amplifier may comprise any one of a number of commercially available limiting-amplifier integrated circuits, for example, a limiting-amplifier front end of an FM IF amplifier and detector integrated circuit. The limiting-amplifier is operated so that the input voltages provided to it are in the order of magnitude of broadband noise generated internally by the limiting-amplifier stages. Accordingly, the limiting-amplifier stages encode the differentiated analog signal and the internally generated noise signal into an extrema coded signal, i.e., a signal wherein the times of occurrence of extrema are represented as transitions of a binary signal. Because of the high gain of the limiting-amplifier stages, these stages perform infinite clipping. The extrema coded signal contains information sufficient to enable substantial reproduction of the original analog signal therefrom.

Abstract: A system for converting analog input waveforms into digital signals is disclosed. The system reduces the bit rate required for the transmission of signals over a transmission channel such that the reproduced analog signals at the receiver are perceived still to be of subjectively high quality to the human sensory system, e.g., the human ear. The system includes an extrema coder for encoding only the times of occurrence of extrema, or maximum and minimum values in the input analog waveform, including the times of occurrence of naturally occurring or injected substantially random, broadband noise. The output of the extrema coder is coupled to an interface circuit, which in one embodiment, wherein a delta modulator digitizing stage is used, comprises an integrator. The output of the interface circuit is fed to a digitizing stage, e.g., in one embodiment, a delta modulator. The output of the digitizing stage is then coupled to the transmission channel for transmission to the receiver.

Abstract: High-frequency broadband noise (at frequencies above the lower-frequency analog information signal) is actually required for this system which transforms the information-plus-noise signal (FIG. 2a) into a binary-coded pulse-width-modulated signal (FIG. 2c) whose modulation represents the original information and noise. Such coding uses broadband infinite clipping to enhance the information to noise ratio, and also enhance the dynamic-range capability. A second embodiment synchronizes the binary-coded signal to a signal clock. Enhanced intelligibility for the hearing-impaired is discussed.