Showing papers on "Keying published in 1974"

Digital Amplitude-Phase Keying with M-Ary Alphabets

Abstract: Signal sets employing amplitude and phase keying (APK) with large alphabets conserve bandwidth and do not require as high a signal-to-noise ratio (SNR) as phase-shift keying (PSK). Twenty-nine empirically generated APK sets with M -ary alphabet sizes from 4 to 128 are investigated to determine optimum designs. Selected sets are compared on the basis of a symbol-error-probability bound for both average and peak SNR. Results are presented in the form of symbol error curves. The degradation caused by nonlinearities in a typical TWT amplifier is examined. The effects of AM-AM and AM-PM distortion on APK are presented as a function of power backoff for single-carrier operation (when APK is at the greatest disadvantage compared with PSK). Modem implementation methods, including carrier phase reconstruction techniques, are discussed for basic APK designs.

Burst frequency shift keying data communication system

Abstract: A communications system for transmission of low density digital data from a plurality of transmitters to a common receiver. It is a burst-mode frequency shift keying (FSK) communication system useable with a master antenna television (MATV) system that minimizes mutual interference between outputs of a large number of transmitters individually located with TV sets. The transmitters are combined with converters for transmission of programs through the system to individual TV sets as controlled by the users, and with information such as TV channel in use, room number identification, and specialized information such as completion of maid service, fire, and burglary alarms transmitted back through the system. In one system the transmitters use a carrier frequency of 12MH z , a frequency at the lower end of the passband of a coax system with FSK modulation at an equivalent switching rate of 20KH z and modulation index of 5 accepting a RF channel loading of up to 700 simultaneous users.

Generation of a switching signal for the chroma keying of color video signals

Abstract: Generation of a switching signal for the chroma keying of color video signals, in which generation the voltage level of the switching signal becomes a maximum for a selected hue. The switching signal corresponds, when an adjustable voltage level is exceeded, to a specific color saturation of the selected hue. This generation is carried out by means of a first and a second color difference signal derived from primary signals of a color signal source, and by means of a sine-shaped and cosine-shaped variable control signal, the variation of which is a function of the angle of the selected hue in a color spectrum. In this generation, the first color difference signal is multiplied by the sine-shaped control signal, and the second color difference signal is multiplied by the cosine-shaped control signal, and the multiplied signals are added to a first signal component.

Voice keying system for a voice controlled musical instrument

Abstract: A voice keying system for a voice controlled musical instrument comprising a frequency responding circuit for responding to an input signal of audio frequency and generating a control signal which corresponds to each of a plurality of frequency bands of input signal and also to a plurality of notes of a musical scale, and a tone generator for generating an output tone signal corresponding to each of the notes of the musical scale. The input signal is converted into the output tone signal having a smaller rate of frequency increment than that of the input signal in each of the frequency bands thereof.

About Optimal Properties of Fast Frequency-Shift Keying

Abstract: The optimum observation interval for phase-continuous frequency-shift keying (FSK) is longer than 2T .

Attenuator network for musical instrument keying system

Abstract: A digital keying system for an electronic organ comprises a voltage divider network consisting of weighted value resistors switched into or out of the circuit by corresponding switches. The network is connected to a tone signal output terminal, and a reversible counter is connected to control the states of conduction of the switches. Closure of a key-operated switch causes clock pulses from an attack clock pulse source to be applied to the reversible counter to selectively control the operation of the switches to shape the attack waveform of tone signals appearing on the output terminal as determined by the pattern of operation of the switches. Upon release of the key, clock pulses from a decay clock generator are applied to the counter to operate it in the reverse direction, establishing a decay envelope for the tone signal in accordance with the pattern of operation of the switches. Provisions are made for terminating the application of clock pulses in either direction when a maximum count for that direction has been reached by the counter.

Electronic musical instrument of voltage-controlled tone production type

Abstract: An electronic musical instrument comprises a playing-board section for generating a voltage signal of one polarity by a depression on the board for determining a tone frequency corresponding to the depressed position and a voltage signal of the opposite polarity by the release of the depression, a comparator for comparing the voltage signal with the ground potential and providing a keying signal, a delay-memory circuit for giving a delay to the voltage signal and holding the voltage until a new depression under the control of the keying signal, a voltage-controlled musical tone synthesizer connected to the delay-memory circuit for generating a musical tone signal of a frequency determined by the voltage, and a delay circuit connected between the comparator and the voltage-controlled musical tone synthesizer for keying the musical tone with a delayed keying signal. An undesirable transient voltage change is prevented effectively by the combination of the delay-memory and the delay circuit.

Contactless speed measuring device for rotating shaft - includes circuit for determining pulse keying ratio and two comparators

Abstract: Generated pulses are registered and the device includes an electronic circuit (5) which determines the pulse keying ration. There are two comparators (17, 18) which are used to compare the actual value (b) of the measured ratio with an upper and a lower limit (C, D)(e) is tripped. The signals from the rotating shaft may be produced by known means which include toothed wheels on the shaft interacting with proximity sensors to produce an AC signal, preferably a square wave. The output from the two comparators (17, 18) passes through an OR gate (26).

Television information display system - for digital information signals received from central control

Abstract: The system employs a central transmitter and a number of remote receiving stations, connected to the latter via a radio or cable link, and each provided with a television receiver, so that the information represented by the received digital signals may be displayed as alpha-numeric characters using a section of the television screen, during the reception of normal television programmes. Preferably the numbers 0 to 9 are transmitted as a number of characteristic frequencies and characters are synchronised with the line and image pulses of he television receiver, via a keying circuit connected to the character generator.

Monophonic electronic musical instrument

Abstract: A monophonic electronic music synthesizer in which keying signals are collected on common note busses and common octave busses and then stored in note latches and octave latches of special design to be reset by a keydown signal only in the absence of a setting keying signal. Tone signals from a top octave tone generator are gated by separate note gates arranged in a high note preference arrangement and controlled by signals stored in note latches. A chain of frequency dividers fed by the gated high select tone signal produces octavely related tone signals which are gated by separate octave gates controlled by keying signals stored in octave latches. A low octave lockout circuit locks out keying signals from all but the highest octave in which a keyswitch is actuated to complete a high select system capable of being readily integrated with a polyphonic organ system using a common control keyboard. A simple voltagecontrolled filter for a synthesizer and a volts per octave circuit fed by octave and note latch outputs are described.

Monophonic electronic musical instrument

Abstract: A monophonic electronic music synthesizer in which keying signals are collected on common note busses and common octave busses with a low note lockout circuit and a low octave lockout circuit to provide unambiguous high note select. Keying signals on note and octave busses are encoded in binary encoding circuits and the resultant binary note and octave words stored in note and octave word latches. Decoding gates fed by the latches gate the high note tone signal and the high octave tone signal after frequency division. Complete circuitry for a synthesizer system, including some alternate embodiments, is shown and described.

Keying mechanism for wind instruments

Abstract: A keying mechanism for wind instruments wherein a second hole is provided for a particular note, such as the E flat on a flute, at the same axial location as the original hole for that note. A mechanical linkage is used to automatically open the second hole when another hole in the instrument is uncovered. In the flute, the mechanical linkage is arranged to automatically open the second E flat hole when the note E or a higher note is fingered, thus providing the proper venting and pitch, and allowing the little finger of the player''s right hand to be used more easily to manipulate other keys.

Adaptive coding for coherent detection of digital phase modulation

Abstract: Although coherent phase-shift keying (CPSK) is an efficient means of transmitting digital signals over carrier systems, it has not enjoyed widespread use at microwave and millimeter wavelengths because of the difficulty of recovering an accurate reference carrier for coherent detection. In this paper, a system is described which requires only a narrow-band phase-locked-oscillator filter for reference carrier recovery. This is accomplished by block-coding and decoding the pulse sequence at the terminals; the recovery of a baseband timing wave is also facilitated by the coding process. It is also shown that: (i) for an arbitrary random input sequence, accurate carrier recovery cannot be achieved with just a narrow-band filter, (ii) for the system described, any input pulse sequence is acceptable, and (iii) there is a maximum error in the phase of the recovered reference carrier which can be controlled by choosing the number of pulses in the coding block and the bandwidth of the recovery filter.

ELF-VLF Applications in Navigation and Communications

Abstract: The principal uses of any portion of the radio spectrum are for navigation and communications Many vlf transmitters are now phase stabilized so that they can be used for navigation as well as signals especially transmitted for navigation, such as those from the Omega system Special applications such as differential Omega, difference frequency Omega and relative Omega are considered navigationally VLF has been a mainstay of fleet communications for over half a century Older on-off keying from fixed transmitters is now being upgraded or phased out in favor of modern techniques such as spread-spectrum or minimum shift keying using TACAMO transmitters or the Sanguine array

Effects of System Inaccuracies on the Probability of Bit Error for Pulsed Communication Systems

Abstract: Digital communication systems using the narrow pulses generated by a mode-locked laser are extremely efficient in their use of average laser power However, these narrow pulses require precise system timing and decision intervals matched to the pulse width This paper extends previous work by Gagliardi in this area to consider the effects of pulse timing errors and pulse width mismatch on the probability of bit error for on-off keying, binary pulse position modulation, and quarternary pulse position modulation formats The general expressions are derived, and a number of examples are plotted

The Distribution of Error Probability for Rayleigh Fading and Gaussian Noise

Abstract: The distribution function of the probability of error in the presence of Rayleigh fading and Gaussian noise is determined for the basic binary modulation schemes of coherent frequencyshift keying (CFSK), noncoherent frequency-shift keying (NCFSK), differential phase-shift keying (DPSK), and coherent phase-shift keying (CPSK). General expressions for the distribution function of error probability are also derived when linear maximal-ratio diversity combining is employed. Results are given for various values of average error probability and various orders of diversity.

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.

Photo-electric organ with chiff

Abstract: An electrical organ in which each of the keys of the organ is mechanically coupled to one single pole single throw electrical switch, and a plurality of said switches are each connected to a plurality of photoelectric tone sources through pulse shaping keying circuits, the keying circuits connected to each key switch being connected in a cascade circuit with the direct current potential source and the photocell of one of the tone sources, the other tone sources having photocells connected to the junctions of keying circuits in said cascade circuit. The tone circuits actuated by a given key of the organ may be at the same frequency or may comprise a chiff tone component or a noise-puff component, or may include a special decay circuit which activates a photocell modulated at a different pitch from the main-tone component.

A new VOX technique for reducing noise in voice communication systems. [voice operated keying]

Abstract: A VOX technique for reducing noise in voice communication systems is described which is based on the separation of voice signals into contiguous frequency-band components with the aid of an adaptive VOX in each band. It is shown that this processing scheme can effectively reduce both wideband and narrowband quasi-periodic noise since the threshold levels readjust themselves to suppress noise that exceeds speech components in each band. Results are reported for tests of the adaptive VOX, and it is noted that improvements can still be made in such areas as the elimination of noise pulses, phoneme reproduction at high-noise levels, and the elimination of distortion introduced by phase delay.