Showing papers on "Keying published in 1981"

Spread-Spectrum Multiple-Access Communications

Abstract: In a direct-sequence spread-spectrum multiple-access communications system several asynchronous signals simultaneously occupy the same channel. Each of the signals employs a signature sequence which is selected to have certain desirable correlation properties. For multiple-access communications the primary goal is to be able to separate the spread-spectrum signals at the receiver even though they occupy the same bandwidth at the same time. This problem is considered in the sections which follow for various forms of direct-sequence spread-spectrum modulation including binary phase-shift keying, quadriphase-shift keying, and minimum-shift keying. The emphasis is on the analysis of system performance rather than on the selection of signature sequences. Hence this material complements the recent paper of Sarwate and Pursley (1980) which examines in detail the problem of signature sequence selection.

Electrical connector keying means

Abstract: Electrical connector of the type comprising a plug and a receptacle has changeable keying means. Keying means comprises axially extending latent slots in the hood of the receptacle and grooves on the surface of the plug which receive a key. Slots can be obtained from the latent slots by removing a thin wall section in the hood. A key is then placed in the corresponding groove in the plug so that the key is received in the slot when the parts are mated. Several latent slots are provided in the receptacle hood to permit a plurality of keying arrangements.

Data communication system

Abstract: A data communication system for general purposes having a new ternary carrier frequency shift keying (TCSK) signal The system is applied to a utility load control by transmission of a sub-carrier of an FM broadcast channel It is decoded by a receiver, SCA decoder, TCSK filter and a two level or binary converter and used to communicate to a pre-programmed microprocessor which enables various load control functions to be performed The general system also is given for a QPSK (quadraphase shift keying) operating system A data transmission filter is split between the transmitter and receiver and is operated in cascade to give individual interference filtering at each end of the transmission while also providing combined action and wave shaping A high accuracy FM decoder using zero crossing detection enables data recovery with simple circuits A novel random time load restoration circuit for ramp-up is disclosed A fail safe relay operator is also disclosed The TCSK employs a novel 19 character hex code format which is 8 bit microprocessor compatible and directly usable for other purposes such as ASCII message transmission Both QPSK and TCSK systems offer command structures of variable length so as to permit truncation of message and reduce total message transmit time

On the performance of phase-shift-keying systems

Abstract: Coherent phase-shift keying (CPSK) and differential phase-shift keying (DPSK) are widely used modulation methods in digital communications Bandwidth efficiency, good noise immunity, constant envelope, and simplicity of implementation make these schemes particularly attractive for use over the satellite, terrestrial radio and voiceband telephone channels While system analyses abound in the literature, treatment is usually restricted to the additive Gaussian channel Important issues determining ultimate performance, such as the joint effect of intersymbol interference and the acquisition of carrier phase have not been adequately addressed The main purpose of this paper is to develop analytical tools that can be used to assess system performance under practical operating conditions Pure coherent demodulation schemes such as CPSK are ideals which are rarely achieved in practice, and carrier phase must be estimated prior to and/or during data transmission This requires start-up time, as well as added equipment, and the fidelity of the phase estimate ultimately determines performance In contrast, DPSK is independent of carrier phase, since decisions are made on phase differences However, this comes at a price, and it is known that ideal multiphase DPSK suffers an asymptotic performance penalty of 3 dB in signal-to-noise ratio (s/n) over ideal CPSK We develop a new rigorous method for calculating the error rates of both CPSK and DPSK, under a variety of operating conditions In particular, we find that the intersymbol interference penalty for quaternary DPSK is about 1 dB worse in s/n than for CPSK We demonstrate that the detection efficiency of CPSK approaches the ideal, provided that the s/n of the phase-recovery circuit is about 10 dB more than that at the receiver input Alternatively, for the same s/n, a 10-baud phase-locked loop integration time is required to achieve near-ideal performance

Chord entry keying of data fields

Abstract: A keyboard system for chord entry keying of alphanumeric data fields includes decoding logic permitting substantially or near-simultaneous depression of numeric or alpha data keys and entry or function keys. The logic provides a decoding algorithm for resolving simultaneous entries by utilizing one or another rule of time of key depression. Depression of a numeric or alpha key within 60 milliseconds of an entry key is permitted for decoding of the data as the last key of the current data field. In a time frame between 60 and 100 milliseconds, a warning tone is received for purposes of verifying the last data field entry and to allow the operator to monitor timing performance.

Connector keying device

Abstract: This invention relates to the field of electrical connectors, and particularly concerns electrical connectors with multiple contacts requiring keying of the mating connector parts. With prior art devices, when more than one connector pair is used in a system, different connector parts must be chosen which have a different keying configuration for the key and groove. With another prior art device, which uses a single type connector part, it is necessary to sacrifice one contact position in the connectors. The present invention overcomes the deficiencies of the prior art noted above by providing a keying device which permits manufacture and production of a single type of male or female connector part and yet does not require the sacrifice of contact positions within the connector parts to effectuate the keying. The invention therefore provides an improved connector keying device for keying mating first and second connector parts to assure proper connection between the parts and to prevent connection to other connector parts of unlike keying. In accordance with the invention, there is provided a key mount affixed to the first connector part and adapted to receive a key member mounted thereto. An appropriate key member is removably attached to the key mount. A key member receiver is mounted on the second connector part and has a key member-receiving slot therein aligned with and slidingly receiving the key member when the first and second connector parts are mated.

Controlled output composite keying signal generator for a television receiver

Abstract: A circuit for generating a composite keying signal comprises a burst gate circuit and a voltage translating network in a color television receiver also including keyed signal processing circuits and means for deriving horizontal and vertical blanking signals and a horizontal sync signal from a composite color television signal containing a color burst component. The burst gate circuit responds to the horizontal sync signal to develop a burst gate pulse encompassing the burst interval. A voltage level developed by the translating network in response to the horizontal and vertical blanking signals is combined with the burst gate pulse to produce a composite keying signal. The composite keying signal comprises a first pulse component of a desired level as determined by the translating network and ocurring during the blanking intervals, and a second pulse cmponent as provided from the burst gate circuit, superimposed on the first pulse and encompassing the burst interval. Means are also included for inhibiting the output of the keying signal generator during picture intervals of the television signal, to prevent false keying of the keyed circuits in response to keying signals generated by the keying signal generator in the presence of spurious input signals occurring during picture intervals.

Spectrally Efficient Communication via Fading Channels Using Coded Multilevel DPSK

Abstract: This paper investigates the use of multilevel differential phase-shift keying with forward error-correcting coding as a technique for achieving limited bandwidth, yet reliable communication over a class of fading channels. Error rate bounds based on the cutoff rate are computed to show that multilevel modulation can be used to allow significant coding gains, while maintaining or reducing the bandwidth of the transmitted signal.

Electrical keying arrangement

Abstract: An electrical keying arrangement ensures that correctly associated electrical components, such as a circuit board and connector, are interconnected by completing a conducting path which includes two pairs of keying terminals positioned on the components. One pair of uniquely spaced and positioned keying terminals on the edge of the circuit board are strapped together to complete the conducting path through the other pair of keying terminals when the board is inserted in the connector. The path is completed only when the connector keying terminals are similarly, uniquely spaced and positioned. When completed, the path may be utilized to energize a relay which controls the application of power to the circuit board.

Secure communication system having long-term keying variable

Abstract: A secure communication apparatus incorporates a longterm, non-extractable master key variable which is held in common by all terminals. A pseudorandom bit sequence generator within the transmitter provides a binary bit stream which is transmitted unencrypted to the intended receiver. Both terminals simultaneously mix the master variable with the transmitted pseudorandom bit stream in an identical manner to create a common separate working variable which is subsequently used for data encryption and decryption.

Cochannel and Intersymbol Interference in Quadrature-Carrier Modulation Systems

Abstract: A method is presented for determining the performance of a quadrature-carrier modulation system in terms of probability of error in the presence of additive white Gaussian noise, intersymbol interference, and cochannel interference. This method has been applied to determine the error rate of several quadrature-carrier modulation systems using Butterworth receiving filters of different orders. It has been foand that among the different quadrature-carrier modulation systems studied, sinusoidal frequency-shift keying seems to exhibit the best overall performance in a cochannel and intersymbol interference environment. These results are shown through a number of performance curves that provide useful data for the systems designer.

Hard-limited versus linear combining for frequency-hopping multiple-access systems in a Rayleigh fading environment

Abstract: In comparing two proposed frequency-hopping mobile radio systems for digitized speech, Goodman et al. have observed that the system employing multiple frequency-shift keying (MFSK) can accommodate many more users than the one with differential phase-shift keying (DPSK). Besides the difference in modulation methods, the MFSK system uses hard-limited combining while the DPSK one uses linear combining. Upper bounds are obtained on the probability of error for DPSK systems with hard-limited combining and linear combining. These bounds suggest that the DPSK system with hard limiters can support about twice as many users as the original one.

System for mixing two color television signals

Abstract: The specification describes a system for mixing and (chroma keying) two color television signals as a function of the color of one of the color signals, or of a third color television signal. The system comprises an automatic color generator by means of which the color present in a foreground signal at a selectable position on the corresponding television picture is used as a reference for the switching operation. The adjustment of the keying color is thereby considerably simplified.

A study of keying skills and various alphanumeric keyboards

Abstract: The desire to make a permanent record of one's thoughts and conversation has existed for many centuries. The-development of writing instruments was a slow process. It took over 4000 years for the quill pen to replace the reed pen (Mussin, 1980), and it was not until 1785 that the pencil was invented. In 1884,the fountain pen was introduced, which was followed by the more recent development of the ball-point pen('biro') towards the end of the second World War (1944). One of the reasons for the continuing production of writing implements was the requirement for speed. The need to go faster has always been fundamental to Man's existence. For example, as long ago as 63 BC Marcus Tullius Tiro invented a system of shorthand in order to ensure he had a complete record of Cicero's orations. Since then over a thousand systems of shorthand have been devised for the English language alone. This method of abbreviating words provides one approach for speeding up the 'speech-to-text' process. An alternative is to use a keying device. The development of keying devices was similar to the invention of writing instruments, in that initial production was slow, but the number and versatility of devices rapidly increased as their potential was realised. The first 'writing machine' is thought to have been invented in 1714 (Richards, 1964), and during the nineteenth century many typewriters were manufactured. As a result the number of keying devices produced has steadily increased throughout the last 100 years. This trend has continued, during the last two decades and it is hypothesised that many more keyboards will emerge during the 1980's as technology becomes more sophisticated.

Keying block extracting tool

Abstract: An extracting tool (14 ) for extracting a keying block (12) having keying pins (13) extending outwardly therefrom from the terminal pins (11) of a backplane (10) of an interconnection system. A keying pin seizing mechanism is retained on a mounting card (27) dimensioned to fit between the rails 17 and 18 of a guide frame normally holding a circuit board. The seizing mechanism comprises a pair of adjacent vise blocks (15, 16) having aligned holes (19) to correspond to the locations of the keying pins (13). When the card (27) is fully inserted in the guide frame, the keying pins (13) of the keying block (12) pass through the aligned holes (19) of both vise blocks (15, 16). The latter blocks have opposing parallel faces (20, 21) lying at an angle to the axes of the keying pins (13). A finger operated screw mechanism (23, 24, 30) is provided to draw one vise block (15) against the other (16), a resultant force caused by the wedge action of the vise block parallel faces causing a slight lateral movement of one block (16). A slight shear stress is thus applied to the keying pins (13) to firmly grip them. The mounting card (27) along with the thus seized keying block (12) may then be withdrawn from the guide frame.

Method and circuit for time-correction of digital switching signals

Abstract: A time correction value for each digital switching signal is determined and a set of switching control signals is formed which produce a progressive switching of the digital signal as a function of the time correction value. Each time correction value is stored until the following digital switching signal. The method improves chroma keying in digital color television systems.

Data-related apparatus with a speech-synthesizer output device

Abstract: An audible output device disclosed herein for use in electronic calculators or the like is able to distinguish between audible messages at the time of keying input information and at the time delivering output information reflecting results of operations, for example. The audibel output device relies upon a speech-synthesizer technique which can be implemented with a digital LSI device.

Word processor of japanese sentence

Abstract: PURPOSE:To enable the practice of keying, by switching the discipline mode displaying key characters on the display unit and conventional document forming mode, through the provision of the mode switching key, in the Japanese language word processor. CONSTITUTION:To the central processing unit 1, the keyboard 2, display unit 3, printer 4, document forming mode memory 5, discipline mode memory 6, key character code table memory 7, character code memory 8 character memory 9, and buffer memories 10, 11, 12 are connected. The central processing unit 1 executes the discipline mode program stored in the discipline mode memory 6 when the mode key is depressed at the first keying of key. If no mode key is depressed, the document forming mode program stored in the document forming mode memory 5 is executed.

Camera system for color television

Abstract: A camera system for color television comprising a color television camera, a control unit and a signal processing circuit. As hue signal the signal processing circuit produces a composite color difference signal p(R-Y)+q(B-Y), wherein p and q are combination factors, R and B are color signals and Y is a luminance signal. In addition to the fact that this hue signal can be employed in known manner for chroma keying signal generation it is employed in accordance with the invention to check the registration on display. Herein, there is a choice between three fixed combinations of the combination factors p and q, the signal processing circuit producing a difference signal R-G, R-B and B-G, respectively. For the standardized luminance signal Y=0.59G+0.30 R+0.11 B it follows that: p=8q, p=-q and 7p=3q, respectively.

A Performance Based Evaluation of Keying Logics for Alphanumeric Keyboards

Abstract: : Four keying Logics for the entry of alphanumeric characters were evaluated. The Logics were selected based on their compatibility with current keyboard designs being used for the pilot-aircraft interface involving communications, navigation, and other aircraft subsystems. Each of four groups of seven subjects learned one of the Logics and their performance was recorded on an alphanumeric keying task. Performance measures were keying speed and keying accuracy for alphabetic characters, numeric characters, character strings, and total list. A keying Logic utilizing individual keys (36) for each alphabetic and numeric character was significantly superior to other Logics which used push-button telephone type keyboards, with regard to keying time. With regard to keying accuracy, all Logics performed equally well, with an error rate of approximately 0.5 percent. Significant performance differences among the three matrix keyboard Logics were inconsistent. Of these, one utilizing the telephone arrangement was most accurate. Research is recommended to further examine keying performance in the learned state, as well as under more realistic conditions. (Author)

Modulating circuit of automatic piano player

Abstract: PURPOSE:To attain modulation keying for the low-frequency range and high-frequency range by switching modulation forth and back from the intermediate transition point of a shift register after shifting the output signal of a data reproducing circuit for a standard play tape as many times as a required number of bits. CONSTITUTION:A reproduced signal from tape recorder DR is led to clock pulse generating circuit CG after passing through waveform shaping circuit WS to detect information on a keyboard, volume and pedals. A signal obtained from demodulator D via synchronous separating circuit SDC and the output of pulse generating circuit CG are received by address control counter AC. With signals from word pulse generating counter WPG and another address control counter AC, address latch circuits AL1-AL14 are selected. A demodulated signal from demodulator D is inputted to shift registers SR1 and SR2 and shifted there, so that modulation will be changed over by change-over switch DS.

Indent specification system

Abstract: PURPOSE: To facilitate keying operation greatly by specifying an indention on a line right before a line where indention processing is to be performed on a word processor CONSTITUTION: Sentence data for one line of a word processor is sent to a sentence memory 13 and then displayed on a display device through a CPU12 Sentence data on th 2nd line is inputted with keys and stored in the memory 13 and when the CPU12 sends its output to an indention flag detecting circuit 13 to be inserted between the data on the 2nd and 3rd lines An indention flag set signal is supplied from the CPU12 to the circuit 19 and when feeding to the 3rd line is carried out, a cursor moves to a position where an indent key is operated on the 2nd line, from which a next document is inputted Thus, keying operation is made extremely simple COPYRIGHT: (C)1982,JPO&Japio

Information output device for editing

Abstract: PURPOSE:To enable to make the arrival of print head to the part to be corrected in a short time, by keying the forward or backward space key and character key at first to move the print head to the objective corrected part. CONSTITUTION:To return the print head from P1 to P2, the back space key is keyed and then the character I which is printed at the position where the print head is desired to be stopped, is keyed. This keying is stored in FF2 and the character code of the keying input data is set to the register with the keying signal K of the character key I. When the print head reaches the P3, the character code of I is read out from the edit memory 5, agreement signal is transmitted from the collation circuit 4, the movement instruction control circuit 6 delivers the stop signal to stop the print head. The print head is moved to the objective correction position for addition and insertion with the keying of the back space key and character key again.

Interdigit Keying Intervals on a Membrane Keyboard

Abstract: Fifty-three company personnel were asked to perform several copying tasks using a copier with a flat membrane keyboard. The digit portion of the keyboard was a 3 x 4 keypad. The time it took to key in seven particular two-digit numbers was electronically timed and recorded. The longest keying time was 1.75 s. Age had a reliable effect, though very small. Those over 45 took .1 s longer on average. There was no gender difference in keying times. Various reasons for much longer than average times are discussed. It was also noted that horizontal keying movement seemed faster than vertical movement.

Special effect device

Abstract: PURPOSE:To enhance the visual effect, by comparing the mixed special effect fundamental wave with three comparison levels to generate two square wave signals and by using these signals as keying signals. CONSTITUTION:Mixed special effect fundamental wave signal (d) is compared with three comparison levels (b), (c) and (d) by comparing circuits 6-8. Signal (g) is inputted to gate circuit 13 to obtain signal (h). Signals (g) and (f) are inputted to gate circuit 12 to obtain signal (i). Signals (f) and (e) are inputted to the gate circuit to generate signal (j). Signal (k) is signal (e) itself. Signals (h), (i), (j), and (k) obtained in this manner are used as keying signals to control the picture, thus obtaining a wipe-synthesized output video signal.

Integrated circuit generating keying envelope signals

Abstract: A multiplexed electronic organ utilizing a plurality of integrated circuit chips, each chip time division multiplexing selected keying envelope time constant signals from a switched capacitor time constant generator for two alphabetic notes over the entire frequency range of a spinet or for one alphabetic note over the entire frequency range of the manuals and pedals of a console organ. The same integrated circuit chip is used for both spinet or console organs. Each chip contains a multiplexer circuit which isolates the multiplexed keying envelope output signals from the time constant generator and includes as a coupling means a plurality of switching element arranged into groups. Some of the groups are interconnected to provide the keying envelope time constant signal normally intended for one frequency range to the output associated with a different frequency range.

Burst gate keying and back porch clamp pulse generator

Abstract: A pulse generator for a television receiver produces keying pulses during the video signal back porch interval in order to energize burst gate and brightness control circuitry. The pulse generator is triggered by horizontal sync pulses under strong, noise-free video signal conditions. As the quality of the video signal and the horizontal sync pulses deteriorate due to noise or a weakening signal, the pulse generator is triggered by horizontal retrace pulse in order to provide keying pulses under all video signal conditions.

Pedestal clamp keying pulse generating circuit

Abstract: PURPOSE:To obtain a circuit that suits to be IC-implemented and can secure stable operation against noises, by providing a counting circuit that counts clock pulses of a local subcarrier signal for a fixed time from the trailing edge of a horizontal synchronizing signal. CONSTITUTION:To input terminal 41 of keying pulse generating circuit 30, a local chrominance subcarrier signal is supplied as clock pulses and to input terminal 42, a horizontal synchronizing signal is further supplied as reset pulses. Then, counting circuit 46 counts clock pulses for a fixed time from the trailing edge of the horizontal synchronizing signal and when its count value reaches a fixed value, flip-flop FF5 is reset. Pulses of the fixed count value of counting circuit 52 reset with the output of AND between the output of FF5 and a fly-back pulse supplied from input terminal 33 of no-signal deciding circuit 32 are inputted to latch circuit 55 together with the output of logic circuit 50. According to the state of this latch circuit 55, output pulses of logic circuit 50 or fly-back pulses are sent to keying pulse output terminal 62.