Abstract: A pulse width modulation system for encoding and decoding digital information in which the encoded signal comprises a series of transitions among different signal levels wherein the length of time between transitions determines the value of a digit, so that each digit is represented by one and only one transition.

Abstract: "Method of coding data bits on a recording medium, arrangement for putting the method into effect and recording medium having an information structure."The so-called Miller modulation has the disadvantage that a direct current is generated in the information channel. When this modulation method is used for magnetical or optical recording, the result is that the amplitude values and the zero crossings are deformed as these channels cannot transmit direct current.According to the invention, in order to obtain, a d.c. free modulation, the Miller modulation concept is modified such that sequences of data bits which, after coding, result in the introduction of a d.c. component are coded differently. It appears that, the frequency zero excepted, a good suppression of the response is obtained also in a fairly wide low-frequency portion of the spectrum.

Abstract: A method and apparatus for encoding or decoding data in accordance with a coding format, referred to herein as Y.phi. and which is based on the 3PM coding format. Data encoded in accordance with the Y.phi. format is generated by initially encoding, at a prearranged clocking frequency, binary data in accordance with 3PM format, applying such encoded data to one input terminal of an exclusive OR gate and applying clocking pulses, at the prearranged frequency to the other input terminal. Decoding is similarly achieved by passing the encoded data through an exclusive OR gate. Data encoded according to the Y.phi. format is particularly advantageous on account of the relatively high density of flux transitions which it generates, which may be desirable in certain circumstances particularly if both high and low rate data is to be encoded on the same magnetic tape.

Abstract: Prerecorded audio or video information signals including address data indicating the location of synchronized signals from a plurality of synchronized sources are supplied to a single separation circuit via a switching circuit. The separation circuit, selectively connected to one of the signal sources via the switching circuit, separates the address data from the audio or video information of the connected signal source. A register connected to the separation circuit receives the separated address data which constantly updates the register contents. At least one counter is reset to the contents of the register each time a newly selected signal source is connected to the separation circuit to load the address data of the previously connected signal source into that counter. At regular intervals one binary increment is added to the counter address data so that the counter count value corresponds to the address data of the previously connected signal source.

Abstract: In a data encoding system, digital data is encoded by adjusting the time position of each transition of a rectangular waveform with respect to the immediately preceding transition and in dependence on the value of the data units to be encoded. In one example disclosed, each data unit is a pair of bits of digital data which can therefore have any one of four binary values: 11, 10, 01 or 00. Immediately after a previous transition (T1), the system encodes the next pair of bits and makes the next transition at a time position (T2) dependent on the value of these bits. If the bits are 00, the next transition T2 is spaced from T1 by eight clock periods. If the bits are 01, T2 can occur either seven or nine clock periods after T1. If the bits are 10, T2 can occur either six or ten clock periods after T1. Finally, if the bits are 11, then T2 can occur either five or eleven clock periods after T1.

Abstract: A decoder for Manchester encoded data. Each mid-bit transition of the Manchester encoded data is detected and used to activate a counter which counts pulses from a local clock having a pulse rate eight times the data bit rate. The sixth pulse thus occurs at a point one-fourth of a data bit interval after the start of the next data bit interval. At that point the Manchester encoded data is sampled. Since the clock utilized to produce the Manchester encoded data is at a logic level zero at the sampling time, the sampled logic level of the Manchester data is the same as the logic level of the original data. The sampled logic level is used to recreate the original data level, and so the recreated pulse waveform is of the same wave shape as the original data pulse waveform but lags the original by one-fourth a data bit interval.

Abstract: A binary data encoding and recovery technique for which the encoding is carried out by separating the binary data into successive data words each containing an equivalent number of data bits, generating one or more code signals representative of each data word where each code signal corresponds to a signal change at one of a plurality of signal change positions in a data cell associated with the data word and is spaced from adjacent signal changes in the data cell by at least a prescribed minimum amount, and assuring that succeeding signal changes occurring in a sequence of data cells are spaced at least the prescribed minimum amount by determining whether a signal change in one data cell would be spaced less than the prescribed minimum amount from a signal change in an adjacent data cell and in such event providing for the code signals related to such signal changes to be merged into a code signal corresponding to a signal change positioned at the boundary of the adjacent data cells so that the prescribed mi

Abstract: A circuit for accurately reconstructing the timing information encoded within digital waveforms of the double frequency class includes facilities for restoring the circuit to proper synchronization at start up time or after a burst of noise on an incoming waveform. The circuit first generates three delayed versions of the incoming double frequency waveform. Transitions in the incoming waveform are detected by comparing the incoming waveform with the first delayed waveform and simultaneously comparing the second and third delayed waveforms, the generated transition-event waveforms being identical but out of phase by one half of the bit cell time of the incoming waveform. The two generated transition waveforms are used to form a composite clock which is then used to toggle the state of a D-type flip-flop at one half bit cell intervals.

Abstract: An apparatus for decoding a Manchester encoded waveform is described in wh a gating circuit responds to the mid-cell transitions in the encoded waveform to produce an enabling signal which causes a clock circuit to generate high frequency clock pulses. A programmable counter accumulates the generated clock pulses. If the counter exceeds a clock count threshold set by a multiposition switch before the beginning of the following enabling signal, it causes a storage element to sample the encoded waveform and store the sample to provide an output signal representing decoded data. A second, substantially equivalent circuit decodes timing from the encoded waveform. The multiposition switch provides the apparatus with the capability to decode encoded waveforms of varying frequency.

Abstract: A line protocol format with a low bit overhead provides for the high accuracy, asynchronous exchange of digital signal information between processing units in a supervisory control system having a central processing unit (CPU) and at least one remote processing unit (RPU).

Abstract: For the transmission of data by way of a fiber-optical path, three-bit code words representing eight different signal levels are generated in respective signal periods 2T and are converted into pairs of ternary luminous waveforms of duration T having two possible amplitude levels L (low) and H (high). Each waveform pair includes at least one but not more than two light pulses H, of a width not exceeding T/2, occurring in either of two time positions within a cycle T. At the receiving end, the incoming light pulses are modulated--either before or after conversion into electrical signals--with a ramp signal of recurrence period T which transposes the pulses H to either of two elevated amplitude levels depending upon their time position within a cycle, with the pulses L remaining at a low level. The resulting electrical pulses are integrated over successive periods equal to T and sampled in each of these periods for comparison with predetermined thresholds.

Abstract: A localized-field static magnetizing device consists of a non-magnetic substrate having a magnetic layer thereon that contains a succession of adjoining zones of alternately differing lengths and having magnetic inductions of alternately opposing directions. One of the lengths is much greater than the other and the magnetic layer has a high coercive field.

Abstract: A system for reproducing a recorded binary signal from a recording medium that may be read at varying speeds is disclosed. The recording medium in a magnetic recording medium in which the binary signal was recorded by effecting predetermined alternating flux changes in the recording medium, and in which the distance of separation between consecutively effected predetermined flux changes does not exceed a first predetermined distance and is not less than a second predetermined distance.

Abstract: Apparatus for processing bits of information magnetically recorded on a credit card or similar article. The apparatus includes a slot for receiving the credit card as well as a transducer for reading the bits of information when the card is manually moved thereunder. Circuitry connected to the transducer is operative to read the recorded bits of information. Sensors, provided at each side of the transducer, detect and time the initial movement of the card. An alarm circuit is operative to generate a warning if the card does not proceed at the minimum speed necessary to read the bits of information.

Abstract: In the disclosed method, pre-recorded bit markers are read from a magnetic medium as it is moved by hand at a highly variable speed past a magnetic read head. Pulses of a fixed frequency are counted between the reading of adjacent ones of the bit markers. Magnetic flux is written in one direction on the medium upon the reading of the bit markers; and magnetic flux is written in an opposite direction after a time period equal to a fraction of the number of pulses counted between bit markers times the reciprocal of the fixed frequency. Also disclosed is apparatus for performing the steps of the disclosed method.

Abstract: A digital magnetic recording method dependent only on the spacing between flux changes. The flux change spacing with the length "one" is allotted to binary bit "1", that the flux change spacing with the length "one and a half" is allotted to the binary sequence "01" and that the flux change spacing with the length "two" is allotted to the binary sequence"00".

Abstract: Binary numbers are recorded on a track of a medium in the form of signals of first and second voltage levels, respectively indicating alternate timing signals of uniform time duration t and data signals of variable time duration x. A timing signal is followed by a short data signal to indicate binary zero, by a longer data signal to indicate binary one, and by even longer data signals to indicate the absence of binary data. The signals may be decoded by counting up from zero during each timing signal and down during each data signal such that a positive count-down indicates a binary zero, a relatively small negative count-down indicates a binary one, and a relatively large negative count-down indicates absence of binary data.

Abstract: A demultiplexing method and system is disclosed utilizing a differential duration technique. Data that have been conventionally encoded utilizing a technique wherein variations in time contain the essential information, such as can be accomplished by systems wherein data are encoded by modulating either the spacing between pulses or the width of the pulses, is decoded by differential duration demultiplexing to reduce errors caused by time distortion introduced prior to recovery of the data. Time distortion errors are reduced by sensing both the pulses and intervals following the pulses in the data train and deriving decoded data from the difference therebetween.

Abstract: This disclosure describes a decoding system for decoding and formatting digital data recorded on magnetic tape in the STR ("speed-tolerant recording") format. The digital words are stored in cells of about equal width except that the leading cell of each word, called a "sync" cell, is of double width. Each cell starts with a positive pulse, and a cell detector provides a signal each time this occurs. The apparatus includes a data detector, which analyzes the width of this positive pulse relative to the cell width to determine whether the cell is a 1 bit or a 0 bit. Since the measurement is relative, cell length, i.e., total cell time, is not important. The bit determination is loaded into a shift register. Other apparatus determines the width of the cell, so that a sync cell detector can determine whether a sync cell is present or not. When a sync cell is detected, a pulse is generated which actuates the output buffer register to load the bits from the shift register. Data flows from buffer to a computer.

Abstract: An improved method and apparatus for the storage of binary data on a magnetic surface is described. The binary data to be stored is provided in the form of electrical pulses occurring sequentially at intervals of time T. The method and apparatus provide for exciting a recording head and causing a flux transition at a first predetermined time T.sub.1 during the data pulse interval in order to store a first binary character or, alternatively, for exciting the head at a second predetermined time T.sub.2 for storing a second binary character. A minimum transition separation time T.sub.min equal to the interval period T is established by inhibiting excitation of the head at those times which are separated from another transition by a period of time less than T. A limited maximum transition separation time T.sub.max is provided by shifting the excitation of the head in an interval immediately adjacent an interval during which excitation of the head was inhibited.

Abstract: A system for high-density data recording at low tape speeds receives a unipolar signal representing encoded digital data and transforms it to a bipolar signal having a constant pulse width. The low-frequency response required of the system is minimized because the power spectrum of the signal is altered through a time domain transformation. The narrow bandwidth enables the use of very low tape speeds at high bit packing densities. Tape speeds of 15/32 ips or less at densities about 20 thousand (k) bits per inch (BPI) are possible. The spectrum of the transformed code has no direct current (DC) component which eliminates the need for a base line compensator in the reproducing portion of the system.

Abstract: In a system for recording bits in elements along a moving magnetic medium wherein a first valued bit is represented by a pulse of a first width, length or duration, and a second valued bit is represented by a pulse of a second width, length or duration, there is included the improvement of changing either the first width or said second width when the bit to be recorded and the bit previously recorded have the same value.

Abstract: Circuit and method for electrically recording digital data by identifying the beginning of each cell boundary with a pulse and recording an intercell transition for one binary value and no transition for the other binary value.

Abstract: Serially received data bits represented by the positions of signal-amplitude transitions within bit cells are interpreted by measuring the entire duration of a preceding bit cell and utilizing a fraction of such entire duration to sample for the time of occurrence of the signal-amplitude transition in a succeeding bit cell.