Showing papers on "Keying published in 1972"

High-Capacity Microwave System for Digital Data Transmission

Abstract: A nationwide data network is planned that will employ microwave relay networks for both long-haul and short-haul interconnection. A digital modulation technique has been developed that has the constant level advantage of frequency-shift keying (FSK) systems while retaining the error rate and threshold performance of coherently detected binary or four-phase phase-shift keying (PSK). Occupied spectrum and interference characteristics of a 21.5-Mbit/s data system are compared to the more conventional 600-, 1200-, and 1800-channel message systems.

System for master keying axial pin tumbler locks

Abstract: A system for master keying axial pin tumbler locks which includes providing at least certain of the combination pins with at least two different axially spaced surfaces facing the keyway for cooperating with differently shaped notches in the end of a key advanced through the keyway. In its preferred form, the master keying combination pins are stepped so as to form a cylindrical head portion of relatively small diameter and a base portion of a larger diameter and the keys include stepped notches that permit engagement with either the head portion or the base portion of said combination pin so as to permit two different keys to operate the same pin. The system described may be adaptable to grandmaster keying, great grandmaster keying, etc., as well as master keying.

The Effect of Timing Errors in Optical Digital Systems

Abstract: The use of digital transmission with narrow light pulses appears attractive for data communications, but carries with it a stringent requirement on system bit timing. The effects of imperfect timing in direct-detection (noncoherent) optical binary systems are investigated using both pulse-position modulation (PPM) and on-off keying for bit transmission. Particular emphasis is placed on specification of timing accuracy and an examination of system degradation when this accuracy is not attained. Bit error probabilities are shown as a function of timing errors from which average error probabilities can be computed for specific synchronization methods. Of significance is the presence of a residual or irreducible error probability in both systems, due entirely to the timing system, which cannot be overcome by the data channel.

Amplitude-phase-keying with m-ary alphabets: a technique for bandwidth reduction

Abstract: The spectral occupancy of transmitted digital data can be reduced by employing symbols from an M-ary alphabet. A modulation technique combining both amplitude and phase keying (APK) requires less peak and average power than M-ary PSK to achieve the same symbol error probability. Efficient signal set designs have been found by an empirical search of a large number of candidate sets with a comparison based on symbol error probability. New 8-ary and 16-ary designs are presented which outperform previously suggested designs on both a peak and average SNR basis. The bandwidth efficiency of the principal APK sets and PSK is presented as a function of alphabet size (4-ary to 128-ary) to illustrate the bandwidth-power tradeoff.

Electronic musical instrument keying system with envelope sample memorizing voltage dividers

Abstract: An electronic musical instrument keying system comprises, for each tone signal to be keyed, a keyer constituted by a plurality of voltage dividers and switching elements, and a keyer drive circuit having an n-scale counter and a counter drive pulse generator associated with a key-operated switch. The keyer includes a sequentially changing-over voltage divider network having a common input resistor and a plurality of shunt resistors each with the series-connected switching element, wherein resistance values of the shunt resistors are so selected as to represent the sampled levels of the intended keying envelope for the tone signal, the tone signal being supplied through the input resistor and the output of the keyer being derived from the junction between the input resistor and the shunt resistors. Individual switching elements are sequentially rendered conductive by successive pulses from the counter to successively establish the voltage dividers one after another to determine the tone levels successively, thereby forming an envelope. Key touchresponsive tone level determining circuit constructed by a similar voltage divider network may be used with the keyer to control the input tone signal level to the keyer in response to the depression speed of the key. The keying system eliminates the use of a large capacity of capacitors which are required in RC timing circuits in the conventional system, and facilitates the fabrication in an integrated circuit form by mass production.

Method and apparatus for generating self contrasting character images

Abstract: A subsystem of an apparatus that receives character-representative signals and generates video control signals and keying control signals that are suitable for controlling a scanned display to present contrasting character images. A stroke generator means, responsive to the character-representative signals, generates a stroke of a character to be displayed. The stroke consists of a plurality of time sequential bits corresponding to a sequence of display events and a plurality of code bits that distinguish between contrasting portions of the sequence of display events. A decoding means is responsive to the time sequential bits and the code bits and generates keying control signals and video control signals that are suitable for controlling a scanned display to present contrasted images of characters to be displayed. In a preferred embodiment of the invention, the code bits are representative of the keying and video portions of the sequence of display events. The coding means produces signals that disable the generation of video signal during selected stroke portions, the code bits being determinative of which portions of the display event are to be disabled.

Phase representative digital signal modulating apparatus

Abstract: Apparatus for combining two series of digital numbers from each of two different sources wherein the numbers represent phases of signals and for providing an output indicative of the modulation of one of the signals by the other signal with the output being an analog or digital number signal. The concept generally is shown in detail as applied to a differential phase shift keying transmitter where one of the sources of digital numbers is a time division multiplexed source of two signals and the other is a time base or clocking signal which modulates each of the time multiplexed signals from the first source on a raised cosine basis through the use of a look-up table in the form of a read only memory.

Touch-responsive keying circuit for electronic musical instruments

Abstract: In an electronic musical instrument, tone keyer circuits are respectively controlled by touch-responsive keying circuits. The touch-responsive keying circuit comprises: a key switch having a break contact, a make contact and a movable contact; a first charge-discharge circuit having a charging capacitor and a discharging resistor both connected between the movable contact and the ground; an electrical source +B connected to the break contact; a switching transistor with its base connected to the make contact; and a second charge-discharge circuit being provided between the emitter of the transistor and the ground with a second capacitor and with a series circuit of a second resistor and an normally closed switch which is ganged with the key switch, the capacitor being connected to the keyer circuit. While the movable contact of the key switch travels from the break contact to the make contact, the first charge-discharge circuit is discharged with a predetermined time constant. The switching transistor is brought conductive to the extent responsive to a charged voltage remaining in the first chargedischarge circuit at the time the movable contact touches the make contact. The second charge-discharge circuit is charged through the transistor to establish a keying voltage.

Voltage-isolating, keying arrangement for a power-line carrier system

Abstract: In a power-line carrier system, a keying input circuit is isolated from its corresponding keying output circuit by a light-emitting diode which produces light in response to keying signals, and by a light-sensing transistor which supplies output signals in response to light from the light-emitting diode.

Tone keying circuit for telephone inband signaling system

Abstract: A keying circuit is described that enhances the output level of an oscillatory tone signal source and controls the gating of a tone burst from said source to a telephone transmission line in response to signaling control means. The circuit provides a shunting circuit across the oscillator output which includes switching means to enable or disable the shunting circuit and timing means connected between the switching means and the signaling control means. The timing means disables the switching means for a predetermined time interval that is greater than the dial pulse interval.

Keyed control device for machines and other instrumentalities

Abstract: A keyed control device arranged to measure and control an operating characteristic of a machine or other instrumentality, and at a predetermined measurement of the operating characteristic will function to control the energization of means for interrupting an established control circuit to the machine or instrumentality. The control device includes a plug-in keying unit which limits use of the machine or instrumentality to authorized personnel. The keying unit may contain means for either or both visually and non-visually measuring the operating characteristic of the machine or instrumentality, such as a counter of signal impulses representative of the machine or instrumentality productivity. Upon reaching a predetermined number of operations, means are energizable through suitable control devices to shut down or terminate an operating characteristic of the machine or the instrumentality until such time as the authorized keying unit is replaced by another unit which is preset to permit delivery of the predetermined number of machine or instrumentality operations, or by "recharging" the "discharged" keying unit to a predetermined capacity of deliverable operations.

Apparatus for locating a short-circuit in a d.c. wiring network

Abstract: 1,273,432. Keying oscillators. K. YAMADA. 18 July, 1969 [19 July, 1968; 29 Oct., 1968], No. 36372/69. Heading H3R. [Also in Division G1] The keying of an audio frequency Colpitts oscillator 37 in response to pulses from a detector 31 indicating the presence of pulses in a wiring network (see Division G1) is controlled by an SCR 64 to whose gate the pulses, after amplification and clipping, are applied. The SCR is in the emitter path of an emitter follower TR9 to whose base the output of the oscillator is applied. When the SCR is triggered the audio frequency is passed to an amplifier 38 and thence to loud-speaker 39 to indicate the presence of the triggering pulse.

A Computer Program for Keying Options of Multiple-Choice Tests to Increase Internal Consistency1

Abstract: A high degree of internal consistency is a desirable property for most multiple-choice tests to have. The purpose of the program described is to increase internal consistency by assigning empirically derived weights to the options of each item. A procedure similar to that described was used by Hendrickson (1971) in a successful attempt to increase the internal consistency of subtests of the Scholastic Aptitude Test. Guttman (1941) first suggested that the maximum product moment correlation between a set of categories and a continuous crit-

Advanced Measurement Techniques Study for Digital Systems.

Abstract: : This report summarizes the efforts and results aimed at defining a limit and measurement technique for antenna conducted harmonic and spurious emissions from transmitters with digital modulations. The modulations considered were Frequency Shift Keying, biphase and quadriphase Differential Phase Shift Keying, and Pulse Code Modulation-Frequency Modulation. Derivation of the limit was based on the effect of these modulations on three analog and five digital receiver classes in a typical communication system deployment.

Keying While Listening: The Effect of Input Grouping

Abstract: A study was conducted to explore the effect that the temporal grouping of spoken digits has on keyboard entry. Each subject had to key a series of 12-digit messages in an overlapping manner, i.e., he began keying early in the digit sequence and continued to key previously spoken digits while listening to incoming digits. The digits in a message were either spoken with even spacing or they were grouped into three series of four digits each, with pauses between groups. Total message time was equated for grouped and ungrouped messages. Performance was superior for grouped messages. Memory load, defined as the number of digits received in memory but not yet keyed, was higher for grouped messages. The results are discussed in terms of the division and switching of attention between input and output processes.

Bandwidth efficiency for digital communication via a hard limiting channel

Abstract: Introduction For TDMA operation, the bandwidth efficiency attainable in practice for the transmission of digital data is determined by the burst data rate for a pulse transmitter which has sole access to the finite-bandwidth channel. For a hard-limiting channel, the possible signaling alphabets are based on multiphase shift keying, restricted for implementation convenience to biphase, quadriphase, and eight-phase. The additional degree of freedom of amplitude modulation could be applied in a quasi-linear channel, but this would impose an operationally undesirable requirement for power control on all transmitters.