A modulator for differentially encoded phase-shift keyed digital data is implemented entirely by digital means. Baseband serial binary data are illustratively transformed into dibit pairs which are assigned discrete quaternary carrier-wave phase shifts. A "staircasing" shift register whose weighted outputs are combined to form a quantized phase-modulated carrier wave is advanced by a relatively high-speed counter through a frequency divider network. The division rate of the divider is selectivel...

A hand-held digital compass employs an incremental encoder including a digit code disc and sensor unit which are so interrelated with a logic circuit as to permit automatic referencing of the compass when power is initially applied; and further permits use of an extremely small digit code disc which in cooperation with the sensor unit will permit digital recording of the direction and degree or extent of displacement of the compass in a given direction. The logic circuit employed is self-correct...

A digital tampon is provided which is sufficiently rigid to allow for digital insertion but which subsequently, during use, loses its rigidity to provide comfort when worn and when removed. The tampon comprises a rigidifying element extending longitudinally and disposed centrally with respect to the axis of the tampon. The element is chosen to have a dry resistance to compression sufficiently high enough to allow insertion and a wet resistance to compression, less than the dry resistance, and su...

A digital detector which responds to sinusoidal or square wave input sign to detect the presence of a particular frequency or band of frequencies and provide a selectable digital output indicating the presence of this frequency or band. A gated pulse generator operates in response to the input signals, providing pulses that are counted by a binary counter and sensed by a decoder which detects the presence or absence of the frequencies within the selectable bandwidth limits.

A digital modem comprising a discrete analog/digital converter and digital processor for high-speed digital data transmission by means of analog signals over analog transmission facilities. The analog/digital converter comprises a transmitter section including a digital-to-analog converter and an analog matching interface, and a receiver section including an analog matching interface and analog-to-digital converter. The digital processor comprises a signal processor set, a processor control set ...

The digital multiplier is of the add and shift type with a matrix type input in which a number of serial data words can be applied simultaneously to the multiplier enabling the multiplier to compute simultaneously the sum of a number of products. This multiplier is intended for use in digital filters and single channel coders.

A circuit for filtering electrical waveforms in which the useful information is contained in patterns and spacing of zero-voltage crossings is disclosed. Illustratively, a disk memory system is disclosed in which the voltage peaks developed by the disk memory read-transducers are converted into zero-voltage crossing waveforms by differentiation. To eliminate false zero-voltage crossings caused by noise, the digital filter generates a linear ramp waveform whose magnitude is proportional to the ti...

A digital controller is provided for a process control system having a centralized display of process variables and parameters, which allows an operator to alter some or all of the parameters. The controller includes both a digital display and an analog display. The digital display allows instant response to inquiries concerning a wide number of operating prameters and conditions, while the analog display provides a continuous display of the major variables and parameters.

A magnetic tape recording and reproducing apparatus has a head assembly comprising a plurality of transducing heads, and guide means arranged so that the heads are spaced apart by a distance which is great enough so that only one head is affected by a blemish or dust speck on the tape but yet gives an ability to follow tracks on the tape which are closely packed. The guide means and the heads are disposed so that when the tape is transported across the heads, the heads follow paths which are par...

A digital filter configuration incorporating read-only memories for coefficient storage is disclosed in which substantial reduction in memory requirements is achieved. Two read-only memories are addressed by only three arguments for a second-order filter or five arguments for a fourth-order filter.