US3316358A - Switching circuit for rotary magnetic heads - Google Patents

Switching circuit for rotary magnetic heads Download PDF

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Publication number
US3316358A
US3316358A US281146A US28114663A US3316358A US 3316358 A US3316358 A US 3316358A US 281146 A US281146 A US 281146A US 28114663 A US28114663 A US 28114663A US 3316358 A US3316358 A US 3316358A
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US
United States
Prior art keywords
transistor
transistors
heads
emitter
switch
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US281146A
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English (en)
Inventor
Barrett E Guisinger
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ampex Corp
Original Assignee
Ampex Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to NL132574D priority Critical patent/NL132574C/xx
Application filed by Ampex Corp filed Critical Ampex Corp
Priority to US281146A priority patent/US3316358A/en
Priority to GB13832/64A priority patent/GB1018248A/en
Priority to JP2081864A priority patent/JPS4114023B1/ja
Priority to NL6404284A priority patent/NL6404284A/xx
Priority to DEA46059A priority patent/DE1211257B/de
Application granted granted Critical
Publication of US3316358A publication Critical patent/US3316358A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B15/00—Driving, starting or stopping record carriers of filamentary or web form; Driving both such record carriers and heads; Guiding such record carriers or containers therefor; Control thereof; Control of operating function
    • G11B15/02—Control of operating function, e.g. switching from recording to reproducing
    • G11B15/12—Masking of heads; circuits for Selecting or switching of heads between operative and inoperative functions or between different operative functions or for selection between operative heads; Masking of beams, e.g. of light beams
    • G11B15/14—Masking or switching periodically, e.g. of rotating heads
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
    • H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
    • H03K17/60—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being bipolar transistors
    • H03K17/62—Switching arrangements with several input- output-terminals, e.g. multiplexers, distributors
    • H03K17/6257—Switching arrangements with several input- output-terminals, e.g. multiplexers, distributors with several inputs only combined with selecting means

Definitions

  • This invention relates generally to switching apparatus and particularly to a high speed electronic switching circuit.
  • the invention is directed to an extremely rapid switching circuit that is characterized by the absence of large switching transients during operation.
  • This characteristic is achieved by the use of a selectively actuable clamping device connected to a point in an impedance path, coupling a switch input terminal to a switch output terminal, such that when the clamping device is actuated, variations in an input voltage applied to the input terminal do not appear at the output terminal and conversely when the clamping device is not actuated, input voltage variations do appear at the output terminal.
  • the clamping device includes a pair of oppositely poled transistors, each having their emitters and collectors connected between the p-oint in the impedance path and a clamp reference voltage.
  • the bases of the transistors are respectively connected to opposite output terminals of a binary device, such as a multivibrator, so that for one state of the binary device both transistors are saturated, and for the other state of the binary device, both transistors are cut off.
  • a binary device such as a multivibrator
  • FIGURE 1 is ascheniatic diagram of a portion of a television or wideband recorder in which an electronic switching circuit constructed in accordance with the present invention can be utilized;
  • FIGURE 2 is a schematic diagram illustrating the manner in which the magnetic heads of the wideband recorder of FIGURE 1 are connected to switching means;
  • FIGURE 3 is a circuit diagram illustrating the manner in which switching circuitry constructed in accordance with the present invention can be connected to the magnetic heads of FIGURE 1.
  • FIGURE 1 illustrates a portion of a wideband recorder, such as described in US. Patent No. 2,866,012, that includes a scanning drum 10 carrying magnetic heads H1, H2, H3, and H4, uniformly positioned around the drum It) at intervals.
  • a scanning drum 10 carrying magnetic heads H1, H2, H3, and H4, uniformly positioned around the drum It) at intervals.
  • Rotatable along with the wheel ltl is a slip ring 12.
  • a 'brush 14 is conductively engaged with the slip ring 12 and adapted to couple electrical signals appearing on the slip ring 12 to an output conductor 16.
  • the drum 10 is spaced from a guide 18 such that a magnetic tape 20 can be passed through the gap therebetween. That is, the tape 20 is adapted to be moved in a direction parallel to the axis about which the drum 10 rotates.
  • the heads H1, H2, H3 and H4 successively scan the tape 20 transversely. Magnetic fields oriented on the tape 29 so as to represent desired information initiate an electrical current in the winding (not shown) on each head as the head moves across the tape.
  • serial connection of the head windings is theoretically feasible, in practice, because of noise effects and a slight overlapping of the intervals during which each head traverses the tape, it is not feasible to connect all of the head windings in series. Rather, it is imperative that some type of switching mechanism be associated with the heads so as to assure that adjacent heads do not simultaneously contribute signals to the output conductor 16.
  • An initial and extremely simple switching arrangement is to segment the slip ring such that each segment can be connected to a different head winding.
  • Such an arrangement is unsatisfactory because of the switching speeds required as a result of the desired bandwidth of the system, and because of the size limitations of the slip ring.
  • FIGURE 1 Two electronic switching circuits could be utilized with the heads of FIGURE 1 in the manner shown in FIGURE 2. More particularly, the windings 011 heads H1 and H3 could be connected to a common slip ring 22 while the windings on heads H2 and H4 could be similarly connected to a common slip ring 24. Brushes '26 and 28 respectively associated with slip rings 22 and 24 are connected through a control circuit 30 to an output conductor 32.
  • the control circuit Gil includes switches S1 and S2 which respectively connect brushes 26 and 28 to the output conductor 32.
  • the switches S1 and S2 are under the control of a synchronizer 34 in the control circuit which functions to close the switches S1 and 82 alternately and in synchronism with the rotation of the heads thereby alternately coupling the signals applied to the slip rings 22 and 24 to the output conductor 32. Since opposite heads are connected to the same slip ring, the switching arrangement shown in FIGURE 2 avoids the possibility that overlapping signals will be applied to the output conductor 32.
  • FIGURE 3 illustrates a preferred form of switching circuitry that can be utilized I? in the arrangement of FIGURE 2.
  • the brush .26 is connected through a preamplifier (not shown) to the base of a transistor Q1 and to ground through a resistor 36.
  • the collector of transistor Q1 is connected to a source of negative potential while the emitter thereof is connected through resistor 38 to a source of positive potential.
  • the emitter of transistor Q1 is connected through serially connected resistors 40 and 42 to the base of a transistor Q2.
  • the emitter of transistor Q2 is connected through a resistor 44 to a source of positive potential while the collector thereof is connected to a source of negative potential.
  • transistors Q3 and Q4 are of opposite polarity types.
  • the base of transistor Q3 is connected through a parallel circuit including resistor 46 and capacitor 48 to a first output terminal 50' of a multivibrator 52.
  • the base of transistor Q4 is connected through a parallel circuit consisting of resistor 54 and capacitor 56 to a second output terminal 58 of the multivibrator 52.
  • the resistances 40 and 42 connected in series between the emitter of transistor Q1 and the base of transistor Q2 together with the transistors Q3 and Q4 and associated circuitry comprise the switch S1 referred to in FIGURE 2.
  • the switch S2 connecting the brush 28 to the base of transistor Q2 through a preamplifier is identical to the switch S1. That is, the brush 28 is connected to the base of transistor Q1 and through resistor 36' to ground.
  • the emitter of transistor Q1 is connected through resistor 38 to a source of positive potential and through serially connected resistors 40 and 4 2 to the base of transistor Q2.
  • the junction between resistors 40 and 42 is connected to the collectors of transistors Q3 and Q4 while the emitters of these transistors are connected to ground.
  • the base of transistor Q3 is connected through resistor 46 and capacitor 48 to the first terminal 50 of the multivibrator 52. It is to be noted that transistors Q3 and Q3 are of opposite polarity types.
  • the transistor Q4 is poled oppositely to that of transistor Q4.
  • the base of transistor Q4 is connected through resistor 54 and capacitor 56 to the second output terminal 58 of multivibrator 52.
  • the transistors Q3 and Q4 of switch S1 are both saturated for one state of the multivibrator 52 and are both out off for the opposite state of the multivibrator 52. More particularly, for a first state of the multivibrator 52, a positive potential will be applied to the output terminal 50 and a negative potential will be applied to the output terminal 58 so as to cut off both transistors Q3 and Q4. When transistors Q3 and Q4 are cut off, any potential change at the emitter of transistor Q1 will appear at the base of transistor Q2.
  • transistors in switch S2 are arranged oppositely to those in switch S1, when the transistors of switch S1 are saturated, the transistors of switch S2 will be cut off, and conversely when the transistors of switch S2 are saturated, the transistors of switch S1 are cut off. Consequently, voltage variations appearing at the emitters of transistors Q1 and Q1 will alternately appear at the base of transistor Q2.
  • signals will be successively induced in each head winding as the head traverses the tape 20. That is, initially the current induced in the winding on head H1 will modulate the emitter voltage of transistor Q1 and this modulated voltage will be coupled through resistors 40 and 42 to the base of transistor Q2. Simultaneously, the transistors of switch S2 will be saturated thereby clamping the junction between resistors 40 and 42 so as to prevent any currents induced in the windings of heads H2 and H4 from afiecting the base of transistor Q2.
  • the multivibrator 52 switches state so as to saturate the transistors of switch S1 and cut off the transistors of switch S2. Consequently, the current induced in the windings on head H2 will modulate the voltage on the emitter of transistor Q1 which will appear at the base of transistor Q2. From a voltage standpoint it can be said that when the transistors Q3 and Q4 of switch S1 are saturated, the voltage at the junction between resistors 40 and 42 is clamped thereby preventing voltage variations at the emitter of transistor Q1 from appearing at the base of transistor Q2. From a current standpoint the transistors Q3 and Q4 can be considered as a circuit for diverting (when saturated) the current out of the series path including resistors 40 and 42.
  • the voltage appearing at the base of transistor Q2 will proportionately modulate the transistor Q2 emitter voltage to thereby permit an output signal to be derived across the emitter and collector of transistor Q2.
  • An electronic switch including an input terminal; an output terminal, first and second impedance means directly serially connected between said input and output terminals; and means for selectively clamping the junction between said first and second impedance means whereby signals applied to said input terminal are prevented from appearing at said output terminal, said means for selectively clamping including at least one transistor having its collector and emitter connected between said junction and a clamp reference voltage means.
  • An electronic switch including an input terminal; an output terminal, first and second impedance means directly serially connected between said input and output terminals; and means for selectively clamping the junction between said first and second impedance means whereby signals applied to said input terminal are prevented from appearing at said output terminal, said means for selectively clamping including first and second transistors; means for supplying a clamp reference voltage; and means for connecting the emitters and collectors respectively of said first and second transistors in parallel between said junction and the reference voltage means for preventing said junction from swinging above or below the reference voltage by more than the emitter-collector voltage drop across a saturated transistor; and means for alternately saturating and cutting off said first and second transistors.
  • said means for alternately saturating and cutting off said transistors includes a multivibrator having first and second output terminals; and means respectively connecting said first and second multivibrator output terminals to the bases of said first and second transistors.
  • switching apparatus for successively coupling each of said heads to said output circuit comprising: a like plurality of input circuits, each of said heads connected to an input circuit; a plurality of switches, each of which is uniquely connected to a different one of said input circuits; each of said switches comprising first and second impedance means serially connected between one of said input circuits and said output circuit; and means for selectively clamping the junction between said first and second impedance means whereby signals derived from said input circuits are prevented from appearing at said output circuit.
  • said means for selectively clamping includes first and second transistors; means for providing a clamp reference voltage; and means for connecting said first and second transistors between said junction and the reference voltage means for preventing said junction from swinging above or below the reference voltage by more than the emittercollector voltage drop across a saturated transistor; and means for alternately saturating and cutting off said first and second transistors.
  • each of said input circuits comprises a transistor; means forward biasing the emitter-collector path of said input circuit transistor; and means connecting at least one of said heads to the base of said input circuit transistor.
  • said output circuit comprises a transistor; and means connecting said second impedance means remote from said junction to the base of said output circuit transistor.
  • An electronic switch for switching between first and second input terminals and a common output terminal comprising a first pair of impedances: serially connected between said first input terminal and said output terminal, said first pair of impedances having a first junction therebetween, a second pair of impedances serially connected between said second input terminal and said output terminal, said second pair of impedances having a second junction therebetween, and means for alternately clamping said first and second junctions whereby signals applied to said first and second input terminals are alternately prevented from appearing at said output terminal.
  • An electronic switch comprising first and second transistors each having base, emitter, and collector, a clamp reference voltage source, said first transistor having its emitter and collector connected between said first junction and said reference source, said second transistor having its emitter and collector connected between said second junction and said reference source, and means connected to said bases of said first and second transistors for alternately saturating same.
  • An electronic switch further defined by the means for saturating comprising a multivibrator having first and second output terminals, and means respectively connecting said first and second multivibrator output terminals to the bases: of said first and second transistors.
  • An electronic switch further defined by third and fourth transistors each having base, emitter and collector, said third and fourth transistors being of opposite polarity type to said first and second transistors, said emitter and collector of said third transistor respectively connected to the emitter and collector of said first transistor, said emitter and collector of said fourth transistor respectively connected to the emitter and collector of said second transistor, and means respectively connecting said second and first multivibrator output terminals to the bases of said third and fourth transistors.

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  • Recording Or Reproducing By Magnetic Means (AREA)
  • Electronic Switches (AREA)
  • Television Signal Processing For Recording (AREA)
US281146A 1963-05-17 1963-05-17 Switching circuit for rotary magnetic heads Expired - Lifetime US3316358A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
NL132574D NL132574C (de) 1963-05-17
US281146A US3316358A (en) 1963-05-17 1963-05-17 Switching circuit for rotary magnetic heads
GB13832/64A GB1018248A (en) 1963-05-17 1964-04-03 Improvements in or relating to magnetic tape recorders
JP2081864A JPS4114023B1 (de) 1963-05-17 1964-04-14
NL6404284A NL6404284A (de) 1963-05-17 1964-04-20
DEA46059A DE1211257B (de) 1963-05-17 1964-05-14 Schaltvorrichtung zur Verbindung einer Vielzahl von auf dem Umfang einer Abtasttrommel angeordneten Magnetkoepfen mit einem gemeinsamen Ausgangskreis

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US281146A US3316358A (en) 1963-05-17 1963-05-17 Switching circuit for rotary magnetic heads

Publications (1)

Publication Number Publication Date
US3316358A true US3316358A (en) 1967-04-25

Family

ID=23076131

Family Applications (1)

Application Number Title Priority Date Filing Date
US281146A Expired - Lifetime US3316358A (en) 1963-05-17 1963-05-17 Switching circuit for rotary magnetic heads

Country Status (5)

Country Link
US (1) US3316358A (de)
JP (1) JPS4114023B1 (de)
DE (1) DE1211257B (de)
GB (1) GB1018248A (de)
NL (2) NL6404284A (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3372283A (en) * 1965-02-15 1968-03-05 Ampex Attenuation control device
US3391471A (en) * 1965-05-21 1968-07-09 Petterson Adolf Helmer Tumbler dryers
US3569618A (en) * 1966-11-04 1971-03-09 Nippon Electric Co Switching device for magnetic recording/reproducing apparatus
US5151780A (en) * 1989-03-10 1992-09-29 U.S. Philips Corporation Differential amplifiers

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3077545A (en) * 1960-03-07 1963-02-12 Northern Electric Co Gates including (1) diodes and complementary transistors in bridge configuration, and (2) diodes with parallelled complementary transistors
US3229035A (en) * 1962-09-11 1966-01-11 Ampex Selective recording and display systems for television recorders

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1137075B (de) * 1960-07-28 1962-09-27 Licentia Gmbh Schaltungsanordnung fuer durch Tuansistoren geschaltete Ausgangsglieder, insbesondere Relais, bei der durch Spannungsteiler die Kollektor-spannung des Schalttransistors auf einen zulaessigen Wert herabgesetzt wird

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3077545A (en) * 1960-03-07 1963-02-12 Northern Electric Co Gates including (1) diodes and complementary transistors in bridge configuration, and (2) diodes with parallelled complementary transistors
US3229035A (en) * 1962-09-11 1966-01-11 Ampex Selective recording and display systems for television recorders

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3372283A (en) * 1965-02-15 1968-03-05 Ampex Attenuation control device
US3391471A (en) * 1965-05-21 1968-07-09 Petterson Adolf Helmer Tumbler dryers
US3569618A (en) * 1966-11-04 1971-03-09 Nippon Electric Co Switching device for magnetic recording/reproducing apparatus
US5151780A (en) * 1989-03-10 1992-09-29 U.S. Philips Corporation Differential amplifiers

Also Published As

Publication number Publication date
NL132574C (de)
DE1211257B (de) 1966-02-24
NL6404284A (de) 1964-11-18
GB1018248A (en) 1966-01-26
JPS4114023B1 (de) 1966-08-05

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