Showing papers on "Keying published in 1970"

Wide-band optical communication systems: Part I—Time division multiplexing

Abstract: The purpose of this paper is to consider the theoretical error performance of several digital formats suitable for use with a mode-locked laser source, to discuss the problems of implementing these formats, and to consider the design of an illustrative system. Several techniques for time multiplexing are also described. It is assumed that the transmission medium introduces only additive noise and that the detection process is signal shot noise limited. Among the formats examined the practical choices which can achieve highest information rates with lowest probabilities of error are binary, differential phase shift keying, and binary pulse position modulation. For purposes of illustrating state-of-the-art performance the design of a 4000-mile repeatered binary pulse code modulation intensity modulated system is outlined.

Video mixing/special effects amplifiers

Abstract: Amplifier apparatus for operating on plural video signals to provide signal mixing, special effects and the like employs parallel video signal processing circuits which supply their output signals to a common video mixer. A keying signal processor is included for developing control voltages for separately varying video gain in the video processing circuits on a time shared basis. The composite arrangement thereby allows independent level control for the multi-channel video information vis-a-vis control signals such as synchronizing signals and/or a color burst.

Data Modems with Integrated Digital Filters and Modulators

Abstract: The application of a binary transversal filter as transmitting filter and a digital circuit as modulator makes it possible to construct data transmitters consisting only of transistors and resistors. The modulation distortion, caused by the keying of a low-frequency square-wave carrier, can be compensated by a modification of the transfer function of the transmitting filter, provided the carder frequency is chosen to be a multiple of half the bit rate. This principle makes it possible to realize the whole data transmitter in one single integrated circuit. The binary transversal filter, provided with an analog-to-digital converter, can also be used to construct the data receiver for the greater part with digital circuitry.

Signature storage and retrieval system

Abstract: A SIGNATURE STORAGE AND RETRIEVAL SYSTEM COMPRISES AN ARRANGEMENT WHERE SIGNATURES ARE OPTICALLY SCANNED AND DIGITALLY CODED, AND TOGETHER WITH DIGITALLY CODED CORRELARIVE INFORMATION, SUCH AS BANK ACCOUNT NUMBERS, ARE STORED ON DATA PROCESSING RECORDING MEDIA. A SIGNATURE MAY BE VERIFIED BY KEYING INTO THE DATA PROCESSING FILE THE BANK ACCOUNT NUMBER OR OTHER CORRELATIVE INFORMATION CODE WHICH CAUSES THE DATA PROCESSING EQUIPMENT TO RETRIEVE THE SIGNATURE DATA WHICH IS THEN DECODED, AND THE SIGNATURE IS DISPLAYED ON THE SCREEN OF A CATHODE RAY TUBE.

Electrical musical instrument with ensemble and chief effects and unequal stereophonic outputs

Abstract: An electrical musical instrument for simulating pipe organs, and having a natural ensemble effect, spatial tone-distribution effect, air turbulence effect, wind-pressure-change effect, tracker-keying effect, piano voice keying effect, and exact differently modulated harmonic pitch registers for mutation and compound stops and chiff. These effects are achieved by modulator units coupled between harmonic filtered, tone frequency current sources and a stereophonic amplifier-speaker system which produces outputs having levels of amplitudes which vary differently with respect to each other. The outputs connected to the two speakers have inequalities in amplitudes so that each tone has its own distinctive spatial location. The modulator units comprise insulated gate field-effect transistors which are utilized to modulate the tone frequency currents with different patterns of subsonic frequencies including those producing the simulation of natural air turbulence and wind pressure change. Insulated gate field-effect transistors are also used for switching tone and chiff frequency currents so that the change in amplitude is sigmoid during turn-on and turnoff. RC circuitry in combination with the switching insulated gate field-effect transistors permit tracker keying and piano voice keying.

Communications Efficiency of Certain Digital Modulation Systems

Abstract: The efficiency as measured by data rate per unit bandwidth of certain digital modulation systems is compared. The systems considered are frequency modulation (FM), phase modulation (PM), and linear modulation. The achievable bits per cycle in digital PM and amplitude modulation (AM) at a given signal-to-noise ratio and error rate have been known for some time. In digital FM this quantity can be maximized, a fact apparently first realized by J. R. Pierce at Bell Telephone Laboratories. Rigorous optimizations were later carried out by Mazo, Rowe, and the author. In addition to the comparisons made with other systems, additional details related to the optimization problem in frequency-shift keying (FSK) are also furnished. Whereas previous treatments analyzed a frequency discrimination system, this paper treats the optimum detector. The results indicate very minor differences m efficiency attained by the two different models analyzed. Results are exhibited graphically, showing the relationships between the important system parameters.

Demodulator for two-frequency communication system

Abstract: At the receiving end of a communication system utilizing a lower keying frequency f 1 and a higher keying frequency f 2 for the transmission of information, a counter with N/2 stages is stepped by clock pulses having a cadence Nf 2. The incoming two-frequency wave is converted into a train of signal pulses occurring at the end of each half-cycle, these signal pulses being used to reset the counter which therefore does not generate an output if the signal pulses follow one another at a rate equal to or faster than 1/2f 2. With lower incoming frequencies, the counter sets a flip-flop which is then reset by the next signal pulse and which thereby generates a stepped wave to yield, on integration, a definite DC voltage.

Keying system for electronic musical instruments

Abstract: In an electronic musical instrument having playing keys of a keyboard and associated keyer circuits, the effect of doublecontrol can be obtained by the provision of a keying system including first and second keyer controllers provided for each key to control the respective keyers. The first keyer controller is operative for normal key depression stroke prior to the key''s lowest position, while the second keyer controller is responsive to a depressing force applied to the key during its stay at the lowermost end of its stroke.

Wide-Band Detection of FSK Transmissions in a Three-Component-Two-Path Channel

Abstract: The multipath model evaluated is of a three-component-two-path type. In several space channels we have a directtransmission path and a reflected-transmission path. The direct component can be described as specular, while the reflection is a composition of both a specular component and one that is diffuse. The channel bit error probability for noncoherent wide-band frequency-shift keying (FSK) is obtained for such channels. It is shown that parameters such as rate of fade, Doppler, and data rate relative to the delay between the two transmission paths affects the system performance significantly.

Coherent digital frequency shift keying system

Abstract: A frequency shift generator comprises a single source of high frequency oscillations and a programmable frequency divider. Keyed mark and space input signals serve to select two predetermined divider ratios, one for the mark frequency and the other for the space frequency. The invention provides means for generating stable electrical signals of audio frequency range by means of a coherent technique, that is, one in which the phase relationship of subsequent pulses can be precisely determined.

Keying system capable of producing piano-tone effects for use in electronic musical instruments

Abstract: In a keyboard electronic musical instrument, a keying system is described which includes, per key and associated therewith, a percussive pulse generating circuit for generating a percussive pulse having a peak amplitude responsive to the key depressing speed, a divider circuit consisting of serially connected diodes or resistors which are supplied with the percussive pulse and in response thereto deliver percussive pulses of successively different amplitudes from a highest to a lowest. A plurality of tone keyers are also provided for respectively keying tone signals of different frequencies, which keyers are respectively controlled by the different amplitude percussive pulses delivered from the divider circuit, wherein the higher amplitude pulse controls the lower frequency keyer, etc. Thus, when a key is struck, a composite percussive sound is produced which includes a plurality of different frequency tones, wherein the higher frequency signals decays faster than the lower frequency signals. Thus the sounding effects of a piano are better simulated.

The Effect of Fading on the Performance of a Multihop PCM Radio System

Abstract: The effects of fading on the error-rate performance of a multihop line-of-sight PCM radio system, operated with or without diversity, are theoretically analyzed. A set of approximate formulas for the distribution of error probability has been established. These formulas can be used to determine the necessary carrier-to-noise power ratio in a noncoherent frequency-shift keying or coherent phase-shift keying system in order to meet the specified error probability and percent outage time.

Performance Characteristics of Adaptive/Self-Synchronizing PSK Receivers Under Common Power and Bandwidth Conditions

Abstract: An analytical and numerical investigation of the performance characteristics of partially coherent system techniques which consist of 1) the squaring-tracking loop, 2) the pilot-tone tracking loop, and 3) the differential phase-shift keying (DPSK) technique is discussed. Performance characteristics (error probabilities) are obtained under a unified receiving systems framework, with commonality expressed in terms of the receiver data and reference acquisition channel bandwidths and equal total transmitted power conditions. The modulation addressed is binary phase-shift keying (PSK), operating over a Gaussian noise channel with nonstationary phase characteristics. System performance is expressed analytically, computed numerically, and illustrated graphically with the following conclusions. The squaring-tracking loop technique provides the best performance and closely approximates coherent PSK performance when reference smoothing over several bauds is employed. The performance of the squaringtracking loop system and the DPSK system are comparable within a decibel for tracking loop averaging over 1 baud. Performance of the pilot-tone system depends critically upon the tracking loop bandwidth and the power allocation between pilot carrier and information sidebands. In no case considered does the pilot-tone system outperform the squaring-tracking loop system. On the basis of minimum error rate, the systems can be ranked as follows: 1) the squaring-tracking loop system, 2) DPSK, and 3) the pilottone system. At large signal-to-noise ratios, pilot-tone systems can outperform DPSK.

Chiff circuits for electronic organs

Abstract: In a keyed-photocell electronic organ, two (or more) photocells are keyed with a single, make-break key switch via two (or more) respective RC keying or envelope-control circuits, one of which provides a transient keying pulse to a photocell in order to produce a chiff tone component. The chiff keying circuit includes a series capacitor, the output terminal of which is always clamped to ground by a diode circuit except for a short interval after the key switch is closed during which the level at the output terminal initially jumps and then falls off as the series capacitor charges.

A Random Sampling Approach to the Detection of On-Off Keying

Abstract: A random sampling scheme is developed for the digital detection of on-off keying. The received (bandpass) signal is sampled randomly; the samples are fed to a coincidence detector, where the modulation is extracted. The random sampling approach, in conjunction with the simple coincidence detector, makes possible a bonafide digital receiver capable of operating at (carrier) frequencies as high as the state of the art in analog-to-digital conversion will allow, with bit rates of the order of 1 MHz. Performance characteristics are derived, and some preliminary conclusions are drawn relative to the practicability of the proposed receiver.

Frequency Modulation Using Digital Filtering Techniques

Abstract: A simple unstable second-order digital filter with one variable multiplier can provide a source of frequency-modulated signals. This modulator is readily time-shared and should prove attractive when a large number of transmitters are required. A system consisting of a multiple installation of identical binary frequency-shift keying data transmitters is described and analyzed. A refinement which totally eliminates amplitude and phase discontinuities is also presented.

High bit rate optical transmission using midspan spectral inversion

Abstract: The problem of the phase noise generated by nonlinear effects and chromatic dispersion can limit the transmission distance and the bit rate for phase-shift-keying modulation formats. In this paper, the compensation of the nonlinear and linear effects by a midspan optical phase conjugation (OPC) is studied. First, we show the impacts of chromatic dispersion in an OD8PSK systems (Optical Differential 8-Level Phase-Shift Keying), then a long-haul differential 8-Level Phase-Shift Keying (OD8PSK) transmission simulation is studied in order to compare both the performance of the dispersion compensating fiber (DCF) and the midspan optical phase conjugation. OPC allow to obtain a best recovered of transmitted information especially when compared to a «conventional» transmission system; the latter uses dispersion compensating fiber (DCF). OPC performs better even if we increase the bit rate and the distance. Key words : alternative modulation formats; Optical Differential 8-Level Phase-Shift Keying (OD8PSK); dispersion compensation; fiber optics communications; nonlinear phase noise; optical phase conjugation; spectral inversion.

Musical electronic instrument keying with direct current of plural musical effects

Abstract: An electronic musical instrument is provided with a DC current switching circuit for controlling gates that are disposed between various sources of AC potential of audio signal frequency and conventional voicing circuits and signal-to-sound converting means. The switching circuit is under the control of key switches, voice tab switches, preset voice switches, percussion switches, and repeat switches respectively associated with appropriate circuitry to provide one composite DC keying circuit.

Animation circuit for a musical instrument

Abstract: A plurality of tone generators respectively provide a fundamental frequency and even harmonics of the fundamental frequency to a first signal translating circuit of a musical instrument. The musical 12th or third harmonic, of the fundamental frequency is fed to a second transistor circuit which is interconnected with and shares a common output with the first transistor circuit so that the harmonics of the fundamental frequency beat with the added 12th signal component to obtain an animated effect, which simulates a nominally in-tune pair of vibrating strings. Simultaneous energization of the transistor circuits is provided by a control circuit which is responsive to a direct current keying voltage to render the transistor circuits operative to provide a percussive output envelope, and responsive to an alternating keying voltage to render the transistor circuits operative to provide a sustained output envelope.

Electronic organ keying circuits

Abstract: In a keyed-photocell type electronic organ, two or more photocells are keyed with a single, make-brake switch via two or more respective RC keying circuits having onset and/or decay times corresponding to the tone colors and/or pitches desired. Each keying circuit may control both a first photocell corresponding to a relatively low-pitched, fast-starting tone and a second photocell corresponding to a relatively high-pitched, slow-starting tone.

Selective automatic audio threshold circuit

Abstract: This invention is an electronic system for keying radiophone transmitters in response to audio information and more particularly to a selective automatic audio threshold circuitry with the ability to adapt to environmental noise conditions.

A Circuit Arrangement for a Contactless Keyboard

Abstract: 1,185,676 Touch controlled circuits ELEKTRONISCHE RECHENMASCHINEN KARLMARX-STADT VEB 26 April, 1967, No 19272/67 Heading H3B [Also in Division G4] A circuit includes a non-contact-making keying element comprising passive electrical components connected between a voltage source and an output circuit via a decoupling device, the voltage supplied to the output circuit being controllable by finger pressure on the keying element Fig 1 shows a plurality of such elements arranged to form a keyboard, each element comprising a variable capacitor 2 and resistor 3, connected to transistor amplifiers 7, 8, 9, 10 by way of diodes 4, 5, the connections being such that input information, represented by finger pressure on one of the keying elements is coded in the excess-3-code One or more further transistors may be connected to the keying elements to indicate that the keyboard is operative, the further transistor being biased to operate at a greater finger pressure than the others Capacitor 2 may consist of a metal diaphragm as one plate separated from a fixed metal plate by a layer of barium titanate, a film of glycerine and an air gap Alternatively, both plates may be formed of a conducting plastic or resilient material or such a material may be provided on the inside of the flexible plate Instead of a diaphragm a movable rigid metal member may be provided The key elements may incorporate means for signalling actuation of the key

Noise protected agc circuit with amplitude control of flyback pulses

Abstract: A source of keying pulses which occur in time coincidence with the synchronizing pulse components of a video wave is coupled to the input circuit of an automatic gain control (AGC) transistor. The keying pulses are of a polarity to drive the AGC transistor into conduction to adjust the charge on a capacitor in AGC circuits connected in an output circuit of the transistor. Second and third transistors are connected across the input circuit to control the amplitude of the keying pulses applied to the AGC transistor. The normally conducting second transistor is driven by the video wave, and is responsive to the synchronizing pulse components above a predetermined amplitude, to cut off the second transistor and thereby permit keying pulses to develop across the input circuit and drive the AGC transistor into conduction. The third transistor conducts in response to impulse noise to attenuate the keying pulse, and thus substantially decrease the AGC system gain when impulse noise is present. Additional direct current sources are coupled to the AGC transistor under control of the second transistor to (1) prevent AGC lockout upon occurrence of sudden increases in received signal level under transient conditions and (2) speed the response of the AGC system under nonsynchronized, strong signal conditions.

Error rate for envelope-detected on--off keying in the presence of interference

Abstract: The effects of an interfering carrier and Gaussian noise on envelope-detected on--off keying are analysed. Optimum decision levels with their resulting error rates were found numerically and are presented for a range of interference and noise levels.

Keying circuit for simultaneously switching a plurality of circuits

Abstract: A plurality of circuits employed in an electronic musical instrument and having different time constants are simultaneously switched by a keying circuit according to the present invention which is so organized that the circuits to be switched are arranged in an increasing order of the time constants, a single switch is connected directly to a switching terminal of the firstly arranged circuit having the smallest time constant, and a plurality of diodes are disposed in such a manner that each diode is connected between adjacent switching terminals of the circuits and that the forward direction of the diodes is so arranged as to conduct at a closure of the above said single switch. When the circuits to be switched include one or several groups of circuits having similar time constants, each of such groups of the circuits are commonly connected to a switching terminal and arranged in an increasing order of the time constants to be organized into a keying circuit as described above.