Showing papers on "Keying published in 1979"

Performance of Optical Receivers with Avalanche Photodetection

Abstract: This paper reports the results of a computer study to numerically evaluate the digital performance of an optical receiver with avalanche photodetectors. Exact and approximate APD statistics were implemented and error probabilities in the range l0^{-1} to l0^{-4} were computed. Both shot-noise and receiver-noise limited conditions were examined, and on-off keying, binary pulse comparison, multilevel intensity, and PPM signaling formats are considered.

Receiving circuit in an interference-suppressing communications system comprising narrow-band conventional message modulation and additional pseudo-noise phase shift keying

Abstract: A receiving circuit for an interference-suppressing communications system having a narrow-band conventional message modulation and additional pseudo-noise phase shift keying (PN-PSK), has a pseudo-random generator whose pseudo-random sequence is identical to the pseudo-random sequence provided by the system transmitter. The pseudo-random generator actuates a phase-shift keying element to cancel the phase shift modulation produced at the transmitter. A matched filter or correlation network for correlation of the pseudo-random sequence at the receiver with the pseudo-random sequence contained in the received signal is provided. The message modulation impairs the function of the matched filter or the correlation network. The degrading influence of message modulation is to be eliminated, at least, reduced. To this end, a demodulation circuit is provided which receives the entire received signal and the signal present after removal of the phase-shift keying to provide an input for the matched filter or correlation network. This signal only exhibits the pseudo-noise phase-shift keying contained in the received signal, but no longer has the message modulation.

Digital coherent phase demodulator

Abstract: A digital system for demodulating coherent phase shift keyed signals. Maximum likelihood estimates of the unmodulated phase and rate of change of the unmodulated phase of the received signal relative to a local oscillator signal are used to improve the demodulation process. The maximum likelihood estimates are obtained from measurements of the phase of the received signal relative to the local oscillator signal over a predetermined set of keying intervals. The digital demodulation process permits rapid "lock-on" at low signal-to-noise ratios.

Bit synchronizer with early and late gating

Abstract: This device generates clock pulses which are synchronized with the bit data rate of an input antipodal bit pattern. The device can be used with multiple input data channels whenever such channels are synchronized, i.e., the periodicity of each channel is the same and the phase relationship between channels is fixed. For example, it can be used with QPSK modulation with two input basebands; or with biphase shift keying, frequency shift keying, or other types of modulation with only one baseband input. The circuit uses a form of delay lock loop which estimates the mean zero crossing instant of the input data stream. It compares the zero crossings with early and late gates which are generated on the basis of prior analysis of the input stream. A multiple transition detector circuit is employed when the operating environment is very noisy to inhibit the counting of multiple zero crossings during a combined early gate/late gate period.

Digital Communication Systems in Impulsive Atmospheric Radio Noise

Abstract: Analyses are presented of the performance of binary and M-ary coherent and noncoherent communication systems operating in the impulsive atmospheric radio noise environment. The receiver is usually a maximum likelihood detector for white Gaussian interference and therefore has the form of a parallel bank of matched filters followed by decision circuitry. By employing a Poisson or generalized Shot noise model for the impulsive noise with a suitable probability density function (pdf), closed-form expressions and bounds of error probabilities for M-ary noncoherent and coherent amplitude-shift keying (ASK), phase-shift keying (PSK), and frequency-shift keying (FSK) systems are obtained and the results discussed.

Electronic safety device for motor vehicles - has radar whose pulse width is affected by driving speed and distance of vehicle in front

Abstract: The safety device informs the driver about the distance and relative speed of a vehicle in front of him. It has an antenna transmitting in front radar station operating with short pulses with high keying ratio and a signalling device with lamps informing the driver about the state of all important objects in different distance ranges. The radar pulse width is affected by the driving speed, and is adjusted to the corresp. safety distance.

Organ brass pulse keyer

Abstract: A brass pulse keyer for electronic instruments such as electronic organs wherein the tone during attack is both amplitude modulated and pulse width modulated. The keyer is adapted for large scale integration and comprises a timing capacitor, an electronic switch connected between a source of charging potential and a capacitor and having a control terminal which is connected to the tone input, and a second electronic switch connected in series with the charge voltage, the first switch, and the capacitor and having a control terminal connected to receive the keying envelope. A comparator compares the potential on the capacitor with a reference potential and disables a gating circuit when a compare condition is reached such that the duty cycle may be controlled. As the keying envelope continues towards its maximum, the duty cycle decreases so that a more brilliant tone is achieved. This signal is connected to the input of an analog keyer, which is also controlled by the keying envelope such that amplitude modulation of the tone may also be achieved.

Teletypewriter line keyer with switching current regulator

Abstract: A teletypewriter line keyer with a switching current regulator responsive to a floating, loop current powered voltage comparator used as a loop current monitor. The line keyer, which may have positive and negative line current keying, uses a single current monitor to control positive and negative current regulators responsive to the positive and negative keying respectively. The switching regulators operate within a relatively narrow band centered around the nominal signaling current, with filtering being provided for ripple control. The circuit may also include a keying detector and open loop detector for system monitoring.

Division multiple system for frequency deviation keying frequency

Abstract: PURPOSE:To facilitate an easy time-division use as well as to realize a small size for the device, by multiplying the signal obtained through the bend limitation by the sum of the carrier waves of the mark and space paths to obtain the sum and at the same time eliminating the unnecessary wave.

Keying system for transmitter in radio telephone network - has subscriber appts.sending AF pulses that switch carrier-wave on or off

Abstract: The keying system has its transmitter keyed on by sending short a.f. pulses via the voice link to the transmitter. These pulses are triggered by the microphone button and have a frequency lying within the evaluation range of a voice evaluator in the transmitter's amplifier. The evaluator switches on the transmitter's carrier-wave via a relay. This relay is held during the conversation in the usual way by the voice evaluator and during breaks in the conversation by a timing circuit. At the end of a conversation, the microphone button is released and second a.f. pulses are sent indicating the end of the conversation and causing the relay to release and switch off the carrier wave.

Signal transmission system in channel translating equipment

Abstract: PURPOSE:To prevent the dial signal from being a click noise for the sound signal without a band-pass filter having a rapid attenuation characteristic, by adding one capacitor to the keying circuit to subject the dial signal to low-pass filtering. CONSTITUTION:Dial carrier wave (1) is keyed into keying circuit 11' by dial signal (2) dependent upon turning-on and off operations of the relay contact of the exchange. In this case, since dial signal (2) which is a square wave of 10Hz is applied to keying circuit 11' through low-pass filter 16 which is constituted with a capacitor and the bias resistance of the transistor of the switching part of keying circuit 11', the dial signal is not left as a click noise in the sound signal. Meanwhile, sound signal (5) is modulated by premodulator 13 and has the upper-side band taken out by band-pass filter 14 and is input to modulator 15 together with the dial signal and is modulated and is transmitted to group translating equipment G1.

Generating circuit for border of multiidivision screen

Abstract: PURPOSE:To make it possible to insert a border without making a mix output and border material overlap each other, by inserting the border through keying with a multi-division screen wider than the sum of outputs of pattern generators on a border generating circuit for the multi-division screen. CONSTITUTION:Video inputs 1 and 4 are gated by pattern outputs 14 and 20 for dividing a screen in gate circuits 2 and 5, their video outputs 3 and 6 are mixed by mixer circuit 7, and its output 8 and border material 29 allow keying circuit to insert the border differentially. To pattern generating circuits 11 and 17 for generating a signal controlling gate circuits 2 and 5, delay circuits 13, 15, 19, and 21, AND circuits 23 and 24, and OR circuit 27 are connected so as to generate the key signal with width, and output 28 is inputted to keying circuit 9 with no part where neither a video nor a border is outputted.

Digital input circuit

Abstract: PURPOSE:To prevent the malfunction caused by the double keying by carrying out the data writing to the memory only at the time, when the keying is detected for the first time CONSTITUTION:Key matrix 3 is input part where more than one unit of the switching element carrying out the keying for the operation command are arranged electrically into the grid form And the signal to sweep each row at the grid-type matrix input part is generated by counting the clock pulses delivered from control signal generating part 4 through ring counter 5 With this sweep signal, control part 4 recognizes the keying of the switching element to give the prescribed action In case more than one switching element are keyed between the different rows of the grid at the input part, the key data writing is given to memory 8 only when the keying is detected for the first time Thus, the malfunction caused by the double keying can be preveneted

Generator for shadow super signal for color

Abstract: PURPOSE:To make a stable operation possible even if the color super signal where the luminance signal is not constant is received, by generating a keying signal by the color super signal and by providing a means which delays the super signal. CONSTITUTION:The color super signal from terminal 1' is separated into keying signal S'k and insert signal Sin by separating circuit 15. Signal S'k is processed by delay circuits 5, 6, 8 and 9 and nonmixture adding circuits 7 and 10 and is output as a widened keying signal. Meanwhile, signal Sin is supplied to switch circuit 18 through delay circuit 16 having the same delay quantity as circuits 5 and 6 and delay circuit 17 having the same delay quantity as circuits 8 and 9. The super color signal indicating an arbitrary color is supplied from super color signal generator 13 to circuit 18, and one of signals is selected and supplied to mixing circuit 12. The shadow signal is supplied from shadow color signal generating circuit 14 to circuit 12, and super color signal Ss with shadow is obtained from circuit 12.

User density for 800 MHz microwave mobile radiotelephone communications

Abstract: The results of a user-density analysis for different systems using the 800 MHz frequency band for mobile radiotelephone communications are presented. Our theoretical investigations show that digital phase-shift keying (p.s.k.), double-binary modulation and analogue s.s.b. systems outperform analogue f.m. systems by a factor of approximately two when compared on a user-density basis.

Protective circuit for keying circuit

Abstract: PURPOSE:To protect a keying circuit certainly by detecting an overcurrent and by cutting off the trigger signal of a switching element by the use of a timer.

Generator for multiidivision screen signal

Abstract: PURPOSE:To vary the size of a pattern by independently constituting a plural number of screen-division patterns on a signal generator for dividing the screen of a television set into several by keying. CONSTITUTION:A synchronizing signal, inputted from synchronizing-signal input terminal 1, is made by horizontal-synchronizing signal generating circuit 2 into signal H, which is converted by clock-pulse generating circuit 3 into synchronizing clock CL integer-time high. Horizontal synchronizing signal H and clock CL are supplied to four keying-signal generating circuits 4 to 7. Here, keying signal generating circuits allow horizontal trigger circuits 41 and 42, and R-S flip-flop 43 to generate horizontal pattern signals, and vertical trigger circuits 45 and 46 and R-S flip-flop 47 to obtain vertical pattern signals, and then obtains keying signals from pattern generating circuit 44.

Computer Simulation of VLF Power Amplifiers under Reactive Loading

Abstract: Recent efforts have been made to achieve substantially increased baud rates with the U. S. Navy's very low frequency (VLF) communication system. Because of the constraints imposed by existing transmitter and antenna structures it was necessary to reexamine the operation of every major system component. Each particular VLF transmitter was subjected to an extensive theoretical analysis followed by a detailed on-site measurement program. Following a review of three major systems, Cutler, Lualualei, and North West Cape, a sufficient body of data was available to substantiate the validity of the computer-simulated transmitter analysis presented here. With this method it is possibe to predict frequency-shift keying (FSK) and minimum shift keying (MSK) performance limitations for particular VLF transmitting systems based primarily on the 0 of the antenna at the operating frequency.

Method and apparatus for demodulating a differential phase shift keying signal

Abstract: The invention relates to a method and device for demodulating a digital input signal modulated by differential phase into an output signal representing the significant digital information of the transmitted message. The method includes storing the last two received digital samples of the input signal, to calculate phase suites digital samples of the input signal before and after the last change of initial phase of the input signal, to substitute for the difference between two phases of the same rank the group of bits of the corresponding output signal. Application to signal transmission systems modulated by differential phase.

Monitoring system for keying

Abstract: PURPOSE:To judge the occurrence of failure and to progress the job under working without delaying, by monitoring the keying time when the display section and the keyboard section have the same channel. CONSTITUTION:When the same channel is exclusively used by connecting the keyboard section 6 and the display section 7 to the input and output unit 4 via the CB-CRT control 5, the KB-CRT controller 5 is provided with the monitor timer. Further, of the keying of the keyboard KB is not made even if a given time is elapsed, the keyboard input instruction under execution at present is ended, the interruption of special status is made to the software, the freezing of the system is avoided due to the absence of operator, the channel is opened after a given time, and after that, the message by the software is freely displayed.

Key region split type electronic musical instrument

Abstract: PURPOSE:To make possible expression of minute performance by providing a key region splitting device whick splits and transmits keying outputs so as to split the key region to upper and lower with the key region splitting position as a boundary. CONSTITUTION:A key region splitting position selecting switch 18 is connected to a 1-level signal source and is provided with a moving contact which is rotation-driven by a revolving shaft and four stationary contacts (a), (b), (c), (d) which contact subsequently to this moving contact, producing the four changeover position outputs corresponding to the split positions on the key region of keying output groups from keying channels 16A, 16B. The gate control signals being output respectively from respective OR gates OG1 thru OG9 are applied to the control input ends of gate circuits GT1 thru GT9 and the respective gate circuits GT1 thru CT9 assume a signal transmission state or conduction state when the gate control signals being applied to the respective control input end assume 1 level.

Holding system of key telephone set

Abstract: PURPOSE:To simplify main-wire transfer operation of key telephone set, by providing an electronic method which holds automatically a main wire. CONSTITUTION:With the key of extension calling device 2b operated, contacts 82 and 84 are made to apply timing pulse T5' to FF70, which set at timeing C10. Its output is supplied to FF73 by way of AND gate 71, so that FF73 will be set. The output of FF73 after delay 74 is applied via inverter 91 to AND gate 75, whose output is cut off. As a result, a timing pulse for writting to shift registers 58 and 59 stored with transfer-destination extension number is not inputted, so that rewrite operation will become impossible. Call is therefore carried on even after the keying of the calling device is finished.

Double keying detection system

Abstract: PURPOSE:To increase the calculation speed through the simple-structure circuit by deciding the presence or absence of the data and carry through the sequential addition of the data obtained from the key input part and thus detecting the double keying. CONSTITUTION:Key input part 11 delivers the operation output of the key which is connected every plural units to m-pieces of the scanning line scanned in sequence by the sampling signal to the common line en bloc with every different scanning line. Then the data delivered through the common line at input part 11 is recognized via RAM3 in the form of the n-bit binary code. The memorized binary codes themselves are added at arithmetic circuit 5, the operation to memorize the code in RAM3 again and is repeated until the carry is produced. And when the carry is obtained, whether the data exists or not within the n-bit is decided through judge gate circuit 10 in order to detect the double keying. Thus, the calculation speed can be increased through a simple-structure circuit.

Some Problems with the Criterion-Keying Approach to Occupational Interest Scale Development.

Abstract: A traditionally used method of keying interest inventories, referred to as criterion-keying, involves selecting items which best distinguish a group of incumbents in a particular occupation from an...