Showing papers on "Keying published in 1975"

Typing Speed, Keying Rates, and Optimal Keyboard Layouts:

Abstract: Many variations on the standard typewriter keyboard have been proposed to save finger motion and speed up input. An analysis of keying times during touch typing showed that the standard layout is o...

Differential Phase-Shift Keying Performance Under Time-Selective Multipath Fading

Abstract: Differential phase-shift keying (DPSK) performance analysis in the presence of multipath is extended to include cases in which the Doppler spread is on the order of the bit rate or greater. As the Doppler spread is increased from zero, the performance degrades below that predicted by Jones [1]. However, as the Doppler spread is increased beyond values on the order of the bit rate, performance improves. In the limit as the Doppler spread approaches infinity, with total multipath power held constant, performance approaches that of ideal DPSK as expected. Bit error rate performance in the presence of time-selective Rician fading is presented along with confirming experimental data obtained with a channel simulator.

Shuttering plates for concrete made from foam or hard plastics matl. - have at vertical and horizontal edges keying features for joining purposes

Abstract: The shuttering panels made from foam plastics or from solid plastics are used for making double wall shuttering units, using panels which have at their vertical ends dovetailed or cylindrical keying slots for accommodating matching locking profiles at the end of adjacent shuttering panels. The horizontal edges have similar keying features and keying slots. The flat walls of these plates have shallow dovetail grooves which taper downwards. These keying features on the panel surfaces are used for attaching layers of plastic. In addition these keying features ensure that the shuttering panels remain firmly in contact with the concrete even if the plastics shuttering panels are distorted due to thermal changes. The concrete which fills these grooves on pouring also prevents upwards floating of these lightweight shuttering panels.

Panel and plural module assembly having mechanical keying and modular plug structure to activate/deactivate automatically bridged load carrying circuits

Abstract: A master structure supports a plurality of independent switching and control units. Insertion of a switching and control unit into the master structure makes electrical connection. Load carrying circuits are automatically bridged by the removal of a unit. A test connector and plug enable in-circuit isolation and test of the electrical components within a unit. Mechanical keying insures correct location of units within the master structure.

Video mixing and/or keying system

Abstract: A system for mixing and/or keying video signals includes a number of video signal processors each of which includes a charge-coupled device as a variable delay element to bring about phase coincidence among a plurality of video signals. The amplitude of the delayed video signal from the charge-coupled device is controlled, and the amplitude-controlled video signals are mixed.

Differential phase shift keying demodulator

Abstract: Disclosed is a Differential Phase Shift Keying demodulator employing a Hjlbert filter. Filtered and unfiltered signals are sampled at the symbol rate of an incoming signal, and the sampled signals are each applied to a delay element having a one-symbol period delay. The delayed and the undelayed replicas of the two sampled signals are linearly combined to form the demodulator's output signals.

Effects of randomly delayed visual and auditory feedback on keying performance.

Abstract: An experiment is reported, which assessed the effect on keyboard performance of increasing the length of time intervening between depressing a key and the associated activation of the printer mechanism, termed ‘ delay time’ Sixteen skilled subjects keyed text on a teletype under conditions in which delay time was manipulated as the independent variable. The increase in delay time resulted in significantly worse keying performance as reflected by measures of both speed and accuracy. The data suggested that efficiency of performance was reduced by the delay to both visual and auditory feedback, as well as by the limit imposed on the output rate of the teletype. The results are related to the assumed functions of visual and auditory feedback under normal keying conditions and the advantages and disadvantages of the insertion of a buffer-store between teletype and transmission system are discussed. Ways of reducing performance impairment are proposed.

Transposition apparatus for an electronic musical instrument

Abstract: A transposition apparatus for an electronic musical instrument such as an electronic organ is disclosed. The transposition apparatus permits the playing of a musical score in any desired key regardless of the key actually being played. The apparatus converts the actual keying pattern to a serial bit pattern which is then delayed by a desired number of bit positions. The delayed serial bit pattern is then converted back to a keying pattern to actuate the tone generator of the instrument.

Quaternary phase-shift keying with time delayed channel

Abstract: A digital data communication system employing quaternary phase-shift keying for transmission by a microwave radio link. The digital modulation of the quadrature channel is delayed from the in-phase channel by one-half the time duration of a bit so that the transmitted phase does not experience a quantum shift in excess of 90°. This permits the use of an injection locked oscillator as an amplifier of the microwave transmission.

Seismic group recorder control system

Abstract: In seismic group recording, each seismic trace is initially digitally recorded by a small, portable, magnetic recorder placed near the corresponding seismometer recorder group. A large number of such groups and corresponding recorders are placed over an area or along a profile line, and from a control point, only those specific recorders needed for a given set of record traces are turned on at any time by transmitting a set of coded signals over a communications link which is usually a radio link. The bandwidth restrictions of licensed geophysical radio channels can cause difficulty in this communications system from control point to the various seismometer groups. Accordingly, this disclosure covers an improvement in the communication method employed in a seismic group recorder system. U.S. Pat. No. 3,806,864 teaches the employment of audio frequency encoding on a frequency-modulated band-limited channel with a maximum audio frequency of approximately 3 kilohertz. As initially used, on-off keying of three different tones was employed, due to simplicity. The present system is an improvement employing coherent frequency-shift keying, in which several different audio frequencies, bearing certain relations to each other, are employed. This results in near optimum communication for control of the seismic group recorder system over a voice-grade standard, geophysical licensed radio link.

Circuit arrangement for the transmission and presentation of an analog signal with a video signal

Abstract: A circuit arrangement for the transmission and presentation of an analog signal with a video signal, which permits analog signals which incorporate particular measured values or data, to be subverted into a video signal, to be transmitted with the video signal or, for example, stored on a magnetic tape, and then to be removed as analog values. Concurrently, the analog signals should be presented within the video picture so as to be intelligible to the viewer of the television picture screen. For purposes of blending into the video signal (BAS-signal), there is provided a bar or spike impulse transmitter which is synchronized by the synchronizing impulses of the BAS-signal, which generates bar impulses for producing at least one bar of constant brightness on the television picture screen and transmits this to a mixer stage in which the bar impulses are superimposed on the BAS-signal, and wherein a keying or modulating circuit is arranged between the bar impulse transmitter and the mixer stage to which there is transmitted the analog signal and which so modulates the bar impulses in dependence upon the signal so that the length of the bar on the picture screen corresponds to the analog signal.

PSK Combiners for Fading Microwave Channels

Abstract: The signal-to-noise (S/N) ratio of digital signals can be improved by using diversity transmission, followed by combining at the receive end, resulting in a lower probability of error P(e) . Second-order combining schemes for data signals are presented in this paper. The effect of delay difference in the two channels of a diversity system is analyzed, using four-phase coherent, phase-shift keying (PSK) as an example. For comparison with predicted performance, experimental results are included.

Electronic organ with automatic keying of pedal notes

Abstract: An electronic organ having an automatic pedal keying circuit in which a selected pattern of pedal voice notes is played in response to depression of only a single key, which may be a pedal key. When the automatic circuit is effective, normal pedal voice keying operations are disabled, and pedal voices will be keyed in a selected pattern occurring in a timed sequence. The organ is selectively adjustable between a normal playing mode and the playing mode according to the present invention.

Apparatus for protecting tools of hydraulic presses

Abstract: Apparatus for protecting tools of hydraulically operated fine punch presses of the type having a main piston as well as quick-closing pistons for imparting movement to the press ram. Keying pistons are arranged at the ram in series with and extending in the same direction as the quick-closing pistons to form a keying gap, variable in response to resistance pressure applied to the ram movement at or near the closing operation. A safety stop switch is arranged for detecting the keying gap and for effecting a stoppage of the machine in the event the keying gap is below a predetermined amount indicating an impediment in the path of the ram.

Decision-Directed Automatic Gain Control for MAPSK Systems

Abstract: An automatic gain control (AGC) loop is presented for use with M -ary amplitude- and phase-shift keying (MAPSK) systems The gain control amplifier is regulated by an error signal formed by the difference between the estimated amplitude level and the received amplitude level The AGC performance is thus independent of the short-term average received signal energy AGC loop analysis and simulation is presented for M -ary amplitude-shift keying (MASK) and quadrature amplitude-shift keying (QASK) The AGC is shown to have a negligible degradation on the symbol probability of error for most practical cases A generalized AGC for an arbitrary MAPSK system is also presented

One key chording system for an electronic keyboard instrument

Abstract: A one key chording system for an electronic keyboard instrument of the type in which a single contact keyboard for DC keying of tone signals is employed. A primary keying signal from the single contact keyboard operates one of a plurality of chord gates to produce a chord keying signal which is translated by one of a set of chord logic units into secondary keying signals. The primary and secondary keying signals operate keyers for tone signals corresponding to a musical chord. An inhibit circuit prevents chord gates from responding to secondary keying signals. A mode control circuit switches the single key chording system off to return the instrument to normal operation with multiple key chording.

Data-Derived Symbol Synchronization of MASK and QASK Signals

Abstract: Much has been said in the literature with regard to the problem of establishing symbol synchronization in binary baseband digital communication systems By comparison, the literature contains little information relating to the extraction of symbol sync from multilevel baseband data With the recent interest in multilevel amplitude-shift keying (MASK) and quadrature amplitude-shift keying (QASK) as signaling techniques for multilevel digital communications systems, the problem of providing symbol synchronization in the receivers of such systems becomes paramount This paper presents a technique for extracting symbol sync from an MASK or QASK signal which has been transmitted over an infinite bandwidth white Gaussian noise channel The scheme is essentially a generalization of the data transition tracking loop (DTTL) which has heretofore been used in PSK systems The performance of the loop is analyzed in terms of its mean-squared symbol sync jitter and its effects on the data detection process in MASK and QASK systems

Musical instrument circuit providing celeste and vibrato effects

Abstract: A circuit is shown for changing the frequency of a basic keyed oscillator by controlling the amount of keying voltage reaching the oscillator and the circuit used for vibrato. The purpose of this circuit is the achievement of true "pipe organ celeste" effect without using an added rank or set of oscillators. Circuits are described wherein the harmonic structure of the signal resulting from this modification of a basic keyed oscillator can be made to change by means of controlling the amount of keying voltage reaching the oscillator for the purpose of achieving the desired harmonic structure of the rank when operated in the "non-celeste" mode as opposed to the "celeste" mode. A circuit is also described for amplitude modulation and harmonic structure modulation at the vibrato rate to enhance the vibrato.

Computer with arithmetic unit for arithmetic operations - has memory for storing input and output data of unit

Abstract: At least one keying output mechanism is used to output the contents of the memory in a physical form which is modified by keying. A driver or control circuit is used to drive or actuate the keying output mechanism as a function of the contents of the memory. A buffer circuit can be used to read out and store the equivalent of a place from the contents of the memory and the driver or control circuit can actuate or control the keying output mechanism by means of the output signal from the buffer circuit. The keying output mechanism can contain a number of selectively operated movable rods.

Relay station for radio network - is suitable for relaying operations in several simplex radio networks

Abstract: Each radio network has a frequency channel allocated to it, with different frequency channels in different networks. A counter is stepwise operated by a clock pulse generator. Its stages correspond to the number of networks, and thus of channel in the relay station receiver and transmitter so that all channels are permanently and cyclically connected. The receiver has a device which, when an h.f. carrier reaches it, delivers a signal which stops the clock pulse generator so long as the carrier is present. In order to bridge the sender keying pauses, a delay line releases the clock pulse generator only a certain time after the carrier has disappeared.

On-Line, Real-Time Recognition System on Telegraph Codes: TETAC

Abstract: This paper describes studies of the TETAC system (Teaching Equipment for Telegraph Technology Aided by Computer). The system has been developed for training students at the University of Electro-Communications. TETAC is an intelligent system which recognizes Morse code sent by hand and converts it to letters by means of online and real-time processing. In addition, the system evaluates the qualities of trainees' keying operations; namely, it identifies the students' faults or tendencies. Although TETAC is now in the testing stage, we are confident of the effectiveness of the training and of TETAC's usefulness in modernizing a maritime communication system.

Data transmission system with frequency keying - is for binary signal bits and spacings represented by half-periods of two frequencies

Abstract: The first frequency is a control or keying frequency, and the other is a different keying frequency. The transmitted signal is approx. a sinusoidal signal, whose phase is not interrupted during keying; bits and symbol spacings are fitted into the half period of the corresponding control or keying frequency, and the wave form slope at cross-points is constant. Means are provided for storage of the coded pulse wave and for its conversion into a waveform whose periods corespond to the bits and symbol spacings, so that they can be inserted into half-periods of the corresponding control frequencies; filters convert the produced and so adjusted waveform into a nearly sinusoidal wave.

Periodic rectangular voltage - method for its generation and stabilisation of its keying ratio

Abstract: The variable working point of an amplifier operating as a pulse shaper is so controlled by a voltage derived from the keying ratio, that the latter maintains a constant value, or the variable offset voltage between the two inputs of a differential amplifier operating as the pulse shaper is so controlled by the voltage derived from the keying ration and applied to its second input, that the keying ratio is maintained constant A dc voltage proportional to the output voltage keying ratio is generated by a differential amplifier, whose inputs are controlled by rectangular voltages whose phases differ by 180 deg They are derived from the overdriven amplifier output signal

Counting translation in a telephone junction line - with time measured by keying of a D.C. voltage applied to one of the wires

Abstract: The keying is performed by a device which controls the start and end of counting. A capacitor shunting a keyed resistor is inserted only in the wire carying the counting pulses. Its capacitance is such, that the application of d.c. voltage at the connection beginning immediately makes operative switching means in the preceding selector stage for the counting pulse reception and retransmission. This device also evaluates signals transmitted over the other wire e.g. flashing signals and earth returns; this evaluation is followed by stopping counting pulse generation. An inductance is in series with the keying contacts in the form of an electronic switch.

Heat insulating cover for roof and outside walls - made from rigid foam plastics with keying features at edges

Abstract: The thermal insulating rectangular plates have on their two edges thinner extensions for holding keying features. Two other edges which are at right angles have reentrant keying slots. The keying features are curved profiles which are pushed on the extended thinner edges of the plates. These keying features are pushed into the locking grooves of adjacent plates. The keying profiles do not cover the whole length of the edge while the grooves cover the whole plate edge length. The keying features are flexible and produce a connection which is able to accommodate tensile forces.