Abstract: An arrangement for reproducing an electric signal from a track on a magnetic record carrier (2) includes a magnetic read head (1) for reading from the track an electric signal and for supplying the electric signal to an output, and automatic equalizer filter (5), including transconductance-capacitor filter (6). The transc-filter (6) has a tuning signal input (8). The equalizer filter (5) has a control signal input (15) and is adapted to automatically equalize the electric signal read from the track in response to a control signal supplied to its control signal input, and to supply an equalized output signal at its output (12). The tuning signal input of the transc-filter is coupled to the control signal input of the equalizer filter. The arrangement further includes a control signal generator (13,16) having an output (16) coupled to the control signal input (15) of the equalizer filter (5), the generator being adapted to generate a control signal and to supply the control signal to its output (16).

Abstract: An encoding device encodes a stream of databits of a binary source signal into a stream of databits of a binary channel signal, wherein the stream of databits of the source signal is divided into n-bit source words, which device includes converting apparatus to convert the n-bit source words into corresponding m-bit channel words in accordance with a conversion of the parity preserve type, where m and n are integers, with m>n. The device further includes control apparatus for carrying out DC-control on the binary channel signal by introducing a freedom of choice in the source-to-channel conversion. A decoding device decodes the channel signal obtained from the encoding device.

Abstract: A device is disclosed for encoding a stream of databits of a binary source signal (S) into a stream of databits of a binary channel signal (C) satisfying a (d,k) constraint, wherein the bitstream of the source signal is divided into n-bit source words (x1, x2), which device comprises converting means (CM) adapted to convert said source words into corresponding m-bit channel words (Y1, Y2, Y2). The converting means (CM) are further adapted to convert n-bit source words into corresponding m-bit channel words, such that the conversion for each n-bit source word is parity preserving (table I). The relations hold that m>n≧1, p≧1, and that p can vary. Preferably, m=n+1.

Abstract: An encoder for encoding a stream of data bits of a binary source signal into a stream of data bits of a binary channel signal, the bitstream of the source signal being divided into smaller n-bit source words (x1, x2) which are converted by a logic circuit converter in the encoder into corresponding m-bit channel words, (y1, y2, y3). The conversion of each n-bit source word is parity preserving (see Table I and FIG. 1). The relations hold that m>n≧1, p≧1, and p can vary. Preferably, m=n+1. In order to comply with (d, k) runlength requirements, certain blocks of 2-bit source words are encoded into particular blocks of 3-bit channel words. A decoder is also disclosed for decoding a channel signal produced by the encoder.

Abstract: The invention proposes an apparatus for encoding an information signal. The information signal can be a (d,k) sequence. The apparatus encodes the (d,k) sequence into a (d+n,k+n) sequence by changing the number of zeroes between each time two subsequent ones in the sequence by n. The information signal can also be a RLL sequence of the type (d,k). The apparatus encodes the signal into a RLL sequence of the type (d+n,k+n) by changing the runlengths by n bitcells each.

Abstract: A device for electromagnetically scanning information tracks on a record carrier, such as an optical tape, via a scanning beam is described. On this tape, information tracks are arranged substantially parallel and substantially transverse to a transport direction of the record carrier. The device is provided with a scanning unit for scanning, with the beam always following parallel scanning paths, and a control system for controlling an angle of the scanning paths with respect to the transport direction, dependent on a tilt signal. According to the invention, the device is provided with angle-measuring means for generating the tilt signal dependent on a tracking error signal which is indicative of a difference between a scanning path and the relevant information track. In addition to a tilt signal, a speed signal may also be derived from the tracking error signal. Both the tilt signal and the speed signal are derived from the tracking error signal in a captured and in a non-captured state of operation.

Abstract: The drive system (210) comprises an electronically commutated motor (220) having three windings (225, 226 and 227). The motor (220) is energized by an energizing circuit (270). The energizing means (270) is controlled by three Hall elements (241, 242 and 243) which supply sensor signals (H.sub.1, H.sub.2 and H.sub.3). The motor comprises a permanent-magnetic part whose position is measured by means of the Hall elements. The drive system (210) comprises a status generator (280) which generates status signals (Q.sub.1, Q.sub.2, Q.sub.3 and Q.sub.4) which are dependent upon the ratio between the actual values of the sensor signals (H.sub.1, H.sub.2 and H.sub.3). The drive system (210) further comprises a multiplexer (290) and an inverter (295) which are controlled by the status signals (Q.sub.1, and Q.sub.2, respectively) in order to generate a position signal (P). A corrected position signal (P') is applied to a comparator (260) to generate an error signal (E).

Abstract: A tape-like record carrier (109) is disclosed which comprises paths (A, B). Each path (A, B) contains substantially parallel tracks (1) the path width (1s) in length and the direction of the tracks is transverse to the longitudinal direction of the path (A, B). The diameters (10) of the paths have various directions. The ends of the paths (1) are overlapping. In these overlapping areas the tracks (1) belonging to the various paths are positioned in interlineated manner. Said record carrier (109) is advantageous in that no time is lost during recording or reading when a path is changed. Furthermore, a recording and reading device is disclosed which are applicable in combination with the record carrier.

Abstract: A scanning device for repeatedly scanning a scanning surface of a record carrier (e.g., a tape) by means of a first and a second scanning spot produced by respective scanning beams. The scanning spots perform synchronous movements along a first and a second scanning path, respectively, having different given scanning directions, as a result of which, the distance, viewed in a direction transverse to the scanning paths, between the first and the second scanning spot changes during scanning. The scanning device can be used in a recording and/or read apparatus which further includes a detection system for converting radiation emanating from the second scanning spot into a corresponding detection signal, and a measurement circuit which derives a position measurement signal indicative of deviation of track pitch based on a deviation in a relationship between the detection signal and a reference signal indicative of the position of the first scanning spot on the first scanning path.

Abstract: An arrangement for producing a digital signal from an input (e.g., analog) signal obtained from a transmission medium. The arrangement includes a variable equalizer for equalizing the input signal as regards magnitude and phase as a function of frequency to produce an equalized signal, an equalizer control signal generator for generating first and second control signals for controlling the variable equalizer and a detector for producing the digital signal from the equalized signal. The arrangement further includes a bit array selector (i.e., a bit sequence detector) for generating one or two selection signals upon detection of one or more specific bit arrays (i.e., bit sequences) in the digital signal, and a sample-and-hold unit which samples one or more portions of the equalized signal under the influence of the one or two selection signals so as to produce at least one first sample value and at least one second sample value.

Abstract: An optical scanning device for realizing in a recording layer of an optical tape a longitudinal path (i.e. pattern) of substantially parallel tracks. The device includes an optical system for focusing a radiation beam at the recording layer, which radiation beam causes a scanning spot to develop on the recording layer. The tracks are formed by the optical tape being cyclically scanned, through use of a polygon mirror, via the scanning spot and displaced relative to the optical system in a direction transverse to the scanning direction. The device further includes an optoelectrical measuring unit for deriving a measuring signal indicative of the track pitch of the successively produced tracks. The velocity of the displacement of the optical tape is controlled as a function of the measuring signal.

Abstract: An optical scanning device for scanning a tape-like record carrier. The device includes an optical system for focusing a radiation beam at the record carrier, which radiation beam causes a scanning spot to occur on the record carrier. The device also includes a rotary polygon mirror which causes the scanning spot to be displaced transversely to the direction of the tape with a specific repetition rate. The tape-like record carrier is moved with a certain velocity in the longitudinal direction of the tape relative to the scanning device. In this manner, the record carrier is scanned in accordance with a track pattern formed by a longitudinal path of substantially parallel tracks which have a substantially constant track pitch and a track direction transverse to the longitudinal direction of the record carrier. During operation, vibrations occur which cause displacements to occur of the scanning spot over the recording layer transverse to the scanning direction.

Abstract: A device for encoding a stream of databits of a binary source signal (S) into a stream of databits of a binary channel signal (C), wherein the bitstream of the source signal is divided into n-bit source words (x.sub.1, x.sub.2), which device includes a converting circuit (CM) adapted to convert the source words into corresponding m-bit channel words (y.sub.1, y.sub.2, y.sub.3). The converting circuit (CM) is further adapted to convert n-bit source words into corresponding m-bit words, such that the conversion for each n-bit source word is parity preserving (table I). The relations hold that m>n.gtoreq.1, p.gtoreq.1, and that p can vary. Preferably, m=n+1. Further, a decoding device is disclosed for decoding the channel signal obtained by means of the encoding device.

Abstract: An arrangement for producing a digital signal from an input (e.g., analog) signal obtained from a transmission medium. The arrangement includes a variable equalizer for equalizing the input signal as regards magnitude and phase as a function of frequency to produce an equalized signal, an equalizer control signal generator for generating first and second control signals for controlling the variable equalizer and a detector for producing the digital signal from the equalized signal. The arrangement further includes a bit array selector (i.e., a bit sequence detector) for generating one or two selection signals upon detection of one or more specific bit arrays (i.e., bit sequences) in the digital signal, and a sample-and-hold unit which samples one or more portions of the equalized signal under the influence of the one or two selection signals so as to produce at least one first sample value and at least one second sample value.

Abstract: Viterbi detector for a channel having a memory length 1, where no more than two survivors with an associated difference metric are updated. In the prior-art Viterbi detector of this type the new difference metric is derived using a saturation function from the previous difference metric. If the amplitude of the received signal differs from the values assumed for the calculation of the difference metric, the performance of the prior-art detector will rapidly degrade. In the detector according to the invention the new difference metric is derived from a saturation function of the previous difference metric, with the size of the linear region being dependent on the magnitude of the amplitude of the received signal.

Abstract: A device for recording n-bit information words on a magnetic record carrier. A 1-bit digital word is affixed to each successive information word. The resulting (n+1)-bit information words are then encoded in an aT precoder into (n+1)-bit channel words (cW) which are recorded on the record carrier. The 1-bit digital words which are affixed are such that the running digital sum value of the output signal of the precoder has a desired pattern as a function of time. Consequently, for example, a pilot signal can be inserted into the channel word data stream which may be used to control tracking during reproduction of the recorded information from the record carrier. The values of a and n are such that a .gtoreq.2 and n.gtoreq.1. Preferably, n<<1, for example, n.ltoreq.10.

Abstract: In a run length limited digital signal of the d,k type, (d+m)-bit digital words are inserted at specific instants in the data stream in a manner such that the signal thus obtained is a run length limited signal of the d,k' type, where k' is greater than or equal to k. This signal is then encoded in an aT precoder, a being an integer such that a .gtoreq.1, and recorded on a magnetic record carrier (21). Such (d+m)-bit digital words are inserted so that the digital sum value of the output signal of the precoder has a desired pattern as a function of time. Thus, for example, a pilot signal can be accommodated in the output data stream of the precoder, which pilot signal can be detected during reproduction of the recorded signal. From this detected pilot signal a control signal can be derived for controlling tracking during reproduction of the recorded signal.

Abstract: Apparatus for recording a digital information signal and an auxiliary signal in information tracks of a record carrier without adding the auxiliary signal to the recorded signal. The apparatus converts consecutive information words of the information signal into channel words in accordance with a channel code such that at least three channel words of mutually different disparities are available for such conversion. Selection of a particular channel word for a given information word is determined by a control signal derived from the auxiliary signal and which controls such selection so that the digital sum value (DSV) of the recorded channel words varies substantially in accordance with the auxiliary signal. The control signal is produced from the difference between the auxiliary signal and the DSV of the channel words.

Abstract: In order to achieve tracking in an arrangement for reproducing an electric signal, in particular a digital signal, from a track of a record carrier (1), the arrangement comprises a generator device (25) for deriving a control signal (C.sub.s). This control signal is applied to positioning means (8). Under the influence of this control signal the positioning means can position the read units (magnetic heads K.sub.1, K.sub.2) relative to the tracks (T.sub.3, T.sub.4) to be read by these heads. The generator device (25) is constructed in such a way that it is possible to derive a control signal (C.sub.2) from the information read from the tracks by the heads (K.sub.1, K.sub.2) without tracking signals being recorded in the tracks.

Abstract: A sampled synchronous transmission signal Vt is represented by a series of samples J at equidistant sampling instants. A computing circuit 5 computes the positions R of the sampling instants relative to the rising edges of a virtual reference clock Cref which is phase-locked to the channel clock. For each sampling instant the position R is determined on the basis of the position R of a preceding sampling instant and a measure Q of the difference in time between the sampling interval T and the period L of the virtual reference clock Cref. From the values of the successive samples J an interpolation circuit 2 derives the positions N of the detection-level crossings by the transmission signal Vt, which crossings represent a fixed phase position of the channel clock. After each detection-level crossing the measure Q of the time difference is corrected by circuit 3 and 4, depending on the difference between the positions N and R.