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Патент USA US3084224

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April 2, 1963
E. JAUERNIK
3,084,214
ELECTRONIC SWITCH FOR ROTATING HEAD RECORDER
Filed Feb. 16, 1961
Mi
oN
Jnven?ar
I
EdmundJauernik
by'kwcwum“
Attorney
ìddlllláé
C
tu@
Patented Apr. 2, i953
2
synchronizing signal, means for deriving by frequency
division lfrom the output of said oscillator a comparison
3,„S4,2l4
ELE‘CTEÜNEC SWH‘CH FÜR RÜTATING
HEAD RECÜRDER
I
Edmund .Iauerniln Darmstadt, Germany, assigner to
Fernseh G.rn.h.H., Darmstadt, Germany
Filed Feb. ilo, 1961, Ser. No. 89,#385
Claims priority, application Germany Feb. 17, 196i)
7 Claims. (Ci. 17h-5.6)
signal repetitive at the periodicity of said synchronizing
signal, means for comparing said comparison signal with
said synchronizing signal to develop an error signal of
which the magnitude represents any discrepancy from a
predetermined phase relation between said synchronizing
and comparison signals, means for applying said error
signal to control the frequency of said oscillator so as at
This invention relates to an electronic sequence switch IO least substantially to maintain said predetermined phase
by means of which a plurality of input circuits may be
relation, means for deriving by repeated binary frequency
connected in non-overlapping sequence to an output cir
division from the output of said oscillator square-Wave
signals of different frequency and polarity, means for
cuit. A particular application for a switch of this kind
exists iu systems for reproducing signals, which have been
recorded upon magnetic tape in a series of transversely
extending tracks, by the use of a plurality of transducer
heads mounted upon a rotating member which become
operative in sequence to recover the signals recorded
combining selected ones of said square-wave signals to
yield a said plurality of complex signals each including
a portion `of maximum excursion recurrent at the perio
dicity of said synchronizing signal and having mutually
exclusive, equal durations together equal to the periodic
time of said synchronizing signal and means for applying
Since the signals
recorded upon successive tracks overlap somewhat, the 20 said complex signals to respective switching devices each
controlling a signal channel connecting an individual one
change-over from the operative head to the next in suc
of said input terminals to said output terminal in such a
cession should take place very rapidly, so that in practice
manner that only the maximum positive-going excursion
it becomes essential to employ an electronic switching
in said complex signals cause said switching devices to
device.
upon successive tracks on the tape.
In order to ensure the correct timing of the switching 25 allow signals to pass.
operations it is usual to derive reference signals from the
rotating member and to use these to develop the switching
impulses `which effect the actual switching operation.
This may be done by making the rotating member black
The special advantage gained by the use of the present
invention is that a plurality of switching operations are
effected with very great accuracy of timing within the
switching period determined by a single reference im
over one-half of its circumference and white over the 30 pulse train.
According to an extension of the invention the com
other half and reflecting light from its surface on to
a photoelectrically sensitive device in which there is thus
produced a periodically liuctuating current of Iwhich the
periodic rate corresponds to the speed of revolution of
the head drum.
From this iiuctuating current the switch
ing impulses for operating the electronic switching ele
ments are derived by frequency multiplication and shap
ing. In this system the initial fluctuating current varies
parison signal derived by frequency division from said
oscillator output is passed through a preferably adjustable
phase shifter before being compared in phase with said
synchronizing signal. The advantage of this arrangement
is that it is then not necessary for the synchronizing sig
nal to have an exactly predetermined phase relation to
the Instants at which the switching operations are re
quired to occur, since the exact adjustment of the phase
to determine the timing of the switching points with the 40 relation may be effected by means of the phase shifter.
The novel features which are considered as character
necessary accuracy.
istie for the invention are set forth in particular in the
In another known system, short reference impulses are
more or less sinusoidally and it is thus diíiicult to use it
therefore employed to control the switching points, these
appended claims. The invention itself, however, both as to
reference impulses being developed, for example, by
l its construction and its method of operation with addi
illuminating a disc which is arranged for rotation with 45 tional objects and advantages thereof will be best under
the rotating member which carries the transducer heads
and is pierced by as many holes as the number of trans
ducer heads. Liuht passing through the holes on to a
stood from the following description of a specific embodi
ment when read in connection with the accompanying
drawing. This drawing represents a schematic diagram
of an electronic switch corresponding to the invention. In
photoelectrically sensitive device generates a correctly
timed succession of switching impulses. A further aper 50 this drawing special circuits known per se are illustrated
in the form of blocks.
ture in the rotating disc cooperates with a further photo
The embodiment illustrated is especially suitable for
electrically sensitive device to generate an additional irn
use in connecting the four transducer heads of a known
pulse occurring once per revolution which serves to en
type of reproducing device for magnetic signals in ap
sure the correct switching sequence. This system suffers
from the disadvantage that the angular distribution of 55 propriate sequence to an output terminal. It will be
assumed that the magnetic head drum rotates at 15,000
the holes used for generating the reference impulses must
revolutions per minute, that is, 250 revolutions per second.
correspond with great accuracy to the angular distribu
The switch operation is controlled by an oscillator l,
tion of the transducer heads on their rotating member.
conveniently a square-wave generator, having for the speed
In addition, the need to generate more than one set of
60 of operation a nominal frequency of 1000 c./s. As indi
impulses leads to increased expense.
cated in the drawing, the oscillator may be a symmetrical
It is therefore a main object of this invention to provide
multivibrator .arranged to develop square-wave output sig
for a system for the purpose set forth -which yields more nals A and B of the opposite polarity. The pulse train
saitsfactory results.
It is a further object of this invention to provide for a
system `of the type mentioned which is comparatively
simple in its structure and reliable in operation.
According to the present invention an electronic switch
for connecting a plurality of input terminals to an out
put terminal in a non-overlapping sequence of which the
A, of which the iirst impulse occurring during each switch
ing cycle is positive-going, is applied to control a binary
dividing stage 2 which again is formed symmetrically and
is arranged to provide square-wave output signals C, D
of opposite polarity and having a common recurrence fre
quency of 500 c./s. Pulse train D, of which the lirst im
periodicity is equal to that of a synchronizing signal 70 pulse occurring at the beginning of a switching period is
negative-going, is applied to control a further symmetrical
comprises an oscillation generator operable at a fre
binary divider 3, which may be identical in construction
quency which is a multiple of the periodicity of said
3,084,214
4
with divider 2. Divider 3 again provides square-wave out
put signals of opposite polarity, which are shown at E
and F. lt will be seen that these impulses commence at a
time which isdelayed with respect tothe beginning of the
switching period by one period of the oscillator 1.
The positive-going impulse trainl E from divider 3 is
applied to a circuit `4 which develops from the broad 250
c./s. impulses which are applied toit, narrow impulses of
the same repetition frequency but displaced in phase with
respect thereto. The narrow impulses G thus developed
are applied to a phase-comparator 5 in_which they are
compared in phase with a `synchronizing signal consisting
of brief impulses H recurrent at the switching cycle peri
odicity. For this purpose the synchronizing signalfmay
be converted in a device 6 into a sawtooth signal I.
may be introduced into the lead by which signal B from
oscillator 1 is taken to control divider 8. The trigger
circuit 19 is arranged to perform a transition only when
the next line synchronizing signal received at terminal 20
occurs after a transition >in signal B.
In order to ensure that binary dividers 7 and 8. always
operate in the correct phase, additional trigger signals are
applied> to these circuits. The trigger signals applied to
divider 7 are derived from vbinary divider 3 while the
synchronizing signal is used to trigger divider 8.
Any necessary adjustment of the phase of the switching
sequence with respect to the movement of the rotary mem
ber carrying the transducer heads may be etïected by
adjusting the phase of the comparison impulse G by
In
means of phase shifter 4. The device by which the syn
the present embodiment, the synchronizing signal will be
chronizing signal H is produced need not- therefore» have
derived from the rotation ~of the rotating member carrying
any very closely adjusted relation to the positions of the
the transducer heads.> The error signal developed by the
transducer heads, since its chief function is to ensure the
phase-comparator 5 is applied to oscillator 1 to control
correct switching sequence.
its frequency of operation in known manner, so that this 20
Although the present invention has hereinbefore been
frequency is maintained exactly at the appropriate multi
particularly described with reference to its application to
ple, in the present case the fourth multiple, of the repetition
reproducing apparatus for magnetically recorded television
rate of the synchronizing signal.
signals, it will- be obvious »that it may equally well be
The output pulse vtrain C from the binary divider Z
applied in all cases where a sequence of switching opera
which is positive-going at the beginning of the switching
tions is to> bel performed in cyclic repetition.
periodI is appliedl to a further binary divider 7, which is
What is claimed ask new and desired to be securedV by
Letters Patent is:
again symmetrically constructed and is preferably identical
l. An electronic switch for connecting a plurality of
with dividers 2 and 3. The divider 7 yields output signals
input terminals to an output terminal in a non-overlapping
K and L, which are 250 c./s. square-wave signals of op
posite polarity and of which the` impulses commence at` the 30 sequence of which the periodicity is equal to that of a
synchronizing signal, comprising an oscillation generator
beginning of aswitching period.
.
operable at a frequency which is a multiple of the perio
The 1-000 c./s. square-wave B .from oscillator Lthe :first
dicity of said synchronizing signal, means for deriving the
pulse from which at the beginning of each switching cycle
is negative-going, is applied to another binary divider'íì
which is again of symmetrical construction and which may
` frequency division from the output of said oscillator a
be of like construction to `dividers 2, Sand 7. The divider
8 yields 500 c./s. square-wave output signals M, N, which
are displaced with respect to signals C, D by one half
synchronizing signal, phase comparator means for com
comparison signal repetitive at the periodicity of said
paring said comparison signal with said synchronizing
Isignal to develop an error signal> of which the magnitude
represents any discrepancy from a predetermined phase
cycle of the oscillator signal.
The 500 c./s. square-wave signals M, N are now super 40 relation between said synchronizing andv comparison sig
imposed upon the 250 c./s. square-wave output signals
E, F and K, L of dividers 3 and 7 respectively in networks
9, 10, 11', 12 to yield the complex signals O, 1)„ Q, R.
It will be seen that the most positive-going excursions
(emphasized by shading )of these complex signals occupy
successive, non-overlapping intervals of time, the sequence
being O, Q, P, R. These complex signals'are used to
controly the switching channels. Each switching channel I.
comprises one of four pentode tubes 13, 14, 15„ 16, which
have a common load impedance 17. The signal grid of
each of switching tubes 13-16 is fed by way of one of
terminals I, Il, Il-I, lV, with the signal developed by one
of the transducer heads, while. signals developed across
na‘ls, means for applying said error signal to control :the
frequency of «said oscillator Iso as at least substantially to
maintain said predetermined phase relation, means for
deriving by repeated binary frequency division from the
output of said'oscillator square-wave signals of different
frequency and polarity, means for combining selected ones
of «said square-wave signals to yield a said plural-ity of
complex signals each `including a- portion of maximum
excursion recurrent at- the periodicity of said synchronizing
signal and having mutually exclusive, equal durations to.
gether equal to the periodic time of said synchronizing
signal, and means for applying said- complex- signals Ito
respective -switching devices each controlling a signal
anode load 17- are 'fed out for use as required by way of an.
channel connecting an individual one of said input ter
of the complex signal applied thereto. Thus during the
minals to an output terminal in a non-overlapping sequence
output terminal 18. Each of switching tubes 13-1-6v is 55 minals «to said output terminal in such a manner that only
the maximum positive-going excursions in said complex
arranged to be inoperative in the absence of an appropri
signals cause said switching devices to allow signals to pass.
aïte posit-ivev potential applied> to the suppressor grid, this
2. An electronic switch for connecting four input ter
potential' being provided by the extreme positive excursion
first quarter of each switching cycle- the tube 13 passes the 60 of which the periodicity is equal to that of a synchronizing
signal, comprising an oscillation generator operable at a
signal from input terminal I to output terminal 18, during
frequency
which is the fourth multiple of the periodicity
the' secondV quarter, the tube 14 passes the signal from
of said synchronizing signal and arranged to deliver anti
input terminall II., during the third quarter, the tube 15 _ phased
lirst and second square-wave signals of which the
passesÁ the signal> from input terminal IVII andv during the
impulses next following »the commencement of a switch
65
fourth quarter of each cycleqthe tube 16 passes the signal
ing cycle arerespe'ctively positive- and negative-going, a
from input terminal IV.
`
.
first binary divider fed with said first square-wave signal
The switching process takes place. with greatrapidity,
and arranged to deliver antipha-sed third and fourth square
the speed- of operation being limited only by the rise-time
wave signals having twicel the periodicity of said synchro
of the switching impulses. VThe switching operation will
nizing signal and of which the impulses next following
therefore not normally be visible in the reproduced tele 70 the. commencement of a switching cycle are respectively
vision picture. However, in order in all circumstances to
positive- and negative-going, a second binary divider fed
avoid the appearance of switching transients in the picture
with said third square-wave signal and arranged to deliver
it is desirable to arrange the switching process to take
place only during a line ilyback interval. `To` this end a
trigger circuit 1-9 of known type Vshown in broken lines
antiphased fifth andV sixth square-wave signals having the
same periodicity as said synchronizing. signal, of which a
«transition is- coincident withv the commencement of a
spessis
,
6
5
switching cycle and of which the impulses next following
chronizing and comparison signals, means for applying
the commencement of a switching cycle are respectively
said error signal to control the frequency of said oscillator
so as at least substantially to maintain said predetermined
phase relation, a fourth binary divider fed with said sec
positive- and negative-going, a third binary divider fed
with said fourth square-wave signal and arranged to deliver
antiphased seventh and eighth square-wave signals, having
the same periodicity as said synchronizing signal, of which
a transition occurs at a time delayed after the commence
ment of a switching cycle by one period of said oscillation
generator, the impulses extant at the commencement of
a switching period being respectively negative- and posi
tive-going, means for deriving from said third binary
divider a comparison signal, phase comparator means for
comparing said comparison signal with said synchronizing
signal to develop an error signal of which the magnitude
represents any discrepancy from a predetermined phase
relation between said synchronizing and comparison sig
nals, means for applying said error signal to control the
frequency of said oscillator so as at least substantially to
maintain said predetermined phase relation, a fourth
binary divider fed with said second square-wave signal
and arranged -to deliver antiphased ninth and tenth square
wave signals having twice the periodicity of said synchro
nizing signal of which a transition is delayed with respect
to the commencement of a switching cycle by one-half
cycle of said second square-wave signal and of which the
impulses extant at the commencement of a switching
ond square-wave signal and arranged to deliver anti
phased ninth and tent-h square-Wave signals having twice
the periodicity of said synchronizing sig-nal of which a
transition is delayed with respect to the commencement
of a switching cycle one-half cycle of said second square
wave signal and of which the impulses extant at the com
mencement of -a switching cycle are respectively nega
tive- and positive-going, means for combining said fifth
and ninth square-wave signals to develop a first complex
signal, means for combining said seventh and tenth
square-wave signals to develop a second complex signal,
means for combining said sixth and ninth square-wave
signals to develop a third complex signal, means for corn
bining said eighth and tenth square-wave signals to de
velop a fourth complex signal, and means for applying
each said complex signal to a switching device control
ling the passage of signals from a respective head to
said output terminal.
>
4. An electronic -switch for connecting four heads ar
ranged on a »rotating head wheel of a video tape recorder
to `an output terminal in a non-overlapping sequence of
which the periodicity is equal to that of a synchronizing
cycle are respectively negative- and positive-going, eans
`signal occurring once in each turn of the head wheel,
for combining said fifth and ninth square-wave signals to
comprising an oscillation generator operable at a fre
develop a first complex signal, means for combining said
quency
which is the fourth multiple of the periodicity of
eventh and tenth square-wave signals to develop a second
complex signal, means for combining said sixth and ninth 30 said synchronizing signal and arranged to deliver anti
phased first 4and second square-wave signals of which the
square-wave signals to develop a third complex signal,
impulses next following the commencement of a switch
means for combining said eighth and tenth square-wave
ing cycle are respectively positive- and negative-going, a
signals to develop a fourth complex signal, and means for
first binary divider fed with said first square-wave signal
applying each said complex signal to a switching device
and arranged to deliver antiphased third yand fourth
controlling the passage of signals from a respective said
square-wave
signals having twice the periodicity of said
input terminal to said output terminal.
synchronizing signal and of which the impulses next fol
3. An electronic switch for connecting four heads
lowing the commencement of a switching -cycle are re
ranged on a rotating head wheel of a video tape re
spectively positive- and negative-going, a second binary
corder to an output terminal in »a non-overlapping se
quence of which the periodicity is equal to that of a syn 40 divider fed with said third square-wave signal and ar
chronizing signal occurring once in each turn of the head
wheel, comprising an oscillation generator operable at a
frequency which is the fourth multiple of the periodicity
of said synchronizing signal and arranged to deliver anti
phased first and second square-wave signals of which the 4
impulses next following the commencement o-f a switching
cycle are respectively positive- and negative-going, a first
binary divider fed with said first square-wave signal and
arranged to deliver antiphased third and fourth square
wave signals having twice the periodicity of said synchro
nizing signal and of which the impulses next following
the commencement of a switching cycle are respectively
positive- and negative-going, a second binary divider fed
with said third square-wave signal and arranged to de
liver antiphased fifth and sixth square-wave signals hav
ing the same periodicity as said synchronizing signal, of
which a transition is coincident with the commencement
of a switching cycle and of which the impulses next fol
ranged to deliver antiphased fifth Iand sixth square-wave
signals having the same periodicity as said synchronizing
signal, of which a transition is coincident with the com
mencement of a switching cycle and of which the im
pulses next following the commencement of a switching
cycle are respectively positive- and negative-going, a third
binary divider fed with said fourth square-wave signal
and arranged to deliver antiphased seventh and eighth
square-wave signals, having the same periodicity as said
synchronizing signal, of which 4a transition occurs at
the time delayed after the commencement of a switch
ing cycle by one period of said oscillation generator, the
impulses extant at the commencement of a switching pe
riod being respectively negative- and positive-going,
means for deriving from said third binary divider a com
parison signal repetitive at the periodicity of said syn
chronizing signal, phase comparator means for compar
ing said comparison signal with said synchronizing sig
lowing the commencement of a switching cycle are re 60 nal to develop an error signal of which the magnitude
represents any `discrepancy from a predetermined phase
spectively positive- and negative-Going, a third binary di
vider fed with said fourth square-wave signal and ar
ranged to deliver antiphased seventh and eighth square
relation between said synchronizing and comparison sig
nals, means for `applying said error signal to control the
frequency of said oscillator `so as at least substantially to
wave signals, having the same periodicity as said syn
maintain said predetermined phase relation, a fourth
chronizing signal, of which a transition occurs at the time 65
binary
divider fed with said second square-Wave'signal
delayed after the commencement of a switching cycle
by one period of said oscillation generator, the impulses
extant at the commencement of a switching period being
respectively neßative- and positive-going, means for de
riving from said third binary divider a comparison signal 70
repetitive at the periodicity of said synchronizing signal,
phase comparator means for comparing said comparison
and arranged to deliver antiphased ninth and tenth
square-wave signals having twice the periodicity of said
synchronizing signal of which a transition is delayed with
respect to the commencement of `a switching cycle one
half cycle of said second square-wave signal and of
which ythe »impulses extant at the commencement of a
switching cycle are respectively negative- and positive
signal with said synchronizing signal to develop an error
going, means for applying a trigger signal from said third
signal of which the magnitude represents any discrepancy
binary divider to said second binary divider and for ap
from a predetermined phase relation between said syn 75 plying said synchronizing signal to said fourth binary
3,084,214
8
divider, means »for combining said fifth and ninthsquare
wave signals to develop a Vlirst complex signal», means for
combining saidl seventh and tenth square-wave signals to
develop a second complex signal, means for combining
said sixth and ninth square-wave lsignals -to develop` a third
complex signal, means for combining said eighth` and
tent-h' square-wave signals »to develop a fourth complex
signal, and> means for applying each said complexY signal
to a switching device controlling the passage of signals
from a respective head to said» output terminal.
5. An electronic switch for connecting four heads ar
ranged' on a rotating head wheel of a video tape recorder
to an output terminal in a non-overlappingl sequence of
which the periodicity is equal to that of a synchronizing
signal occurring once in each turn of the head wheel,
comprising an oscillation generator operable at -a fre
quency which is the fourth multiple of the periodicity of
which the periodicity is equal to that of a synchronizing
signal occurring once in each turn of the head wheel,
comprising an oscillation generator operable at a fre
quency which is the fourth multiple of the periodicity of
said synchronizing signal and arranged to deliver anti
phased first and second square-wave signals of which the
impulses next following the commencement of a switch
ing cycle are respectively positive- and negative-going, a
=ñrst binary divider fed with said iirst square-wave signal
and arranged to deliver antiphased third and fourth
square-wave signals having twice the periodicity of said
synchronizing signal and of which the impulses next fol
lowing the commencement of a switching cycle are re
spectively ptositive- and negative-going, aV second binary
divider fed with said third square-wave signal and ar
ranged to deliver antiphased fifth and sixth square-wave
signals having the same periodicity as said synchronizing
said synchronizing signal and arranged to deliver anti
phased ñrst and second square-wave signals of which the
signal, of which a transition is coincident with the com
mencement of a switching cycle and of which the im
impulses next following the commencement of a switch 20 pulses next following the commencement of a switching
ing cycle are respectively positive- and negative-going, a
cycle are respectively positive- and negative-going, a third
first binary divider fed with said iirst square-Wave signal
binary divider fed’ with said fourth square-wave signal
and arranged to deliver antiphased third. and fourth
and arranged to deliver antiphased seventh and eighth
square-wave signals having twice the periodicity of said
square-wave signals, having the same periodicity as said
synchronizing signal and of which the impulses next fol
synchronizing signal, of which a transition occurs at the
lowing the commencement’of a switching cycle are re
time delayed after the commencement of a switching
spectively positive- and negative-going, a second binary
cycle by one period of said oscillation generator, the
divider fed and with said third square-wave signal and
impulses extant at the commencement of a switching pc
arranged to deliver antiphased fifth and sixth square-wave
riod being respectively negative- and positive-going, means
signals having the same periodicity as said synchronizing 30 for deriw'ng from said third binary divider a comparison
signal, of which a transition is coincident with the com
mencement of a switching cycle and of which the im
pulsesv next- following the commencement of a switching
signal repetitive at the periodicity lof said synchronizing
signal, phase comparator means for comparing said com
parison signal with said synchronizing signal to develop
cycle` are respectively Ipositive-and negative-going, a third
an error signal of which the magnitude represents any
binary divider fed Áwith said fourthl square-wave signal 35 discrepancy from a predetermined phase relation between
and, arranged to deliver antiphasedV seventh and eighth
said synchronizing andV comparison signals, means for
square-wave signals, having the same periodicity as said
applying said error signal to control the frequency of
synchronizing signal, of which a transition occurs at the
saidv oscillator so as at least substantially to maintain said
predetermined phase relation, a fourth binary divider
time delayed after the commencement of a switching
cycle by one period of said oscillation generator, the im 40 fed with said second' square-wave signal and arranged
to deliver antiphased ninth and tenth square-wave signals
pulses extant at the commencement» ofv a switching period
being respectively negatiye- and positive-going, means for
having twice the periodicity of said synchronizing signal
deriving from said third binaryV divider a comparison sig
of which a transition is delayed with respect to the com
nal repetitive at the periodicity of said synchronizingsig
mencement of a switching cycle one-half cycle of' said
nal, phase, comparator means lfor comparing said com 45 second' square-wave signal and' of which the impulsesfex
parison signalwith saidsynchronizing signal to develop
tant` atl the commencement of a switching cycle are re
an error signal of which the magnitude represents any
spectively negative- andl positive-going, said fourth binary
discrepancy from a lpredetermined phase relation between
divider including; a trigger circuit yielding av transition in
said' synchronizing andV comparison signals, adjustable
its output signal only when a line synchronizing signal
phase-shifting means included in the signal path by which 50 occurs in a television‘signal applied thereto, means for
combining said ñfth andy ninth square-wave signals to
_said comparison signal is fed to said Vphase comparator,
develop a first complex signal, means for combining said
means for applying said error signal to control the fre.
quency of said oscillator so as at least substantially to
seventh and tenth square-wave signals to develop a sec
ond complex signal, means for combining said sixth and
maintain said predetermined phase relation, a fourth
binary divider fed with said second square-wave signal 55 ninth square-wave signals to develop a third complex sig
and arranged to deliver antiphased ninth and tenth square
nal, means for combining said eighth and tenth square
wave signals to develop a fourth complex signal, and
-wave signals having twicethe periodicity of said syn
means for applying each said complex signal to a switch
chronizing signal ot which a transition is delayed with
ing device controlling'the passage of'signals from a re
respect to the commencement’of a switching cycle one
half cycle of said second square-wave signal andv ofwhich 60 spective head to said output terminal.
the impulses extant at the commencement of a switching
7. A method for connecting a plurality of input ter
cycle are respectively negative- and positive-going, means
for combining said iifth and ninth square-Wave signals to
develop a first complex signal, means for combining said
minals to an output terminal in a non-overlapping se
quence of which the periodicity is equal to that of a syn
chronizing. signal, concerning the steps ‘of generating an
seventh and tenth square-Wave signals to develop a sec 65 oscillation at a frequency which is a multiple of the peri
ond complex signal, means for combining said sixth and
ninth square-wave` signals to develop a third complex sig
nal,- means for combining said eighth and tenth square
wave signals to develop a fourth complexY signal, and
>meansV for applying each said complex signal to a switch 70
ing device controlling the >passage of signals from aV re
spective head to said output terminal.
6. An electronic switch for connecting four heads ar
ranged on a rotating head wheel of a video tape recorder
toY an output terminal in a non-overlapping sequence of 75
odicity of said synchronizing signal, deriving by fre
quency division from said oscillation a comparison signal
repetitive at the periodicity of said synchronizing signal,
lcomparing said comparison signal with said synchroniz
Ving signal, developing an error signal of which the mag
nitude represents any discrepancy from a predetermined
phase relation between said synchronizing and compari
Vson signals, controlling .the frequency ot said oscillation
-by said' error Vsignall so as at least substantially to main
tain said predetermined phase relation,V deriving byre
3,084,214
10
peated binary frequency division from said oscillation
square-wave signals of different frequency and polarity,
combining selected ones ci said square-Wave signals to
yield a said plurality of complex signals each including a
portion of maximum excursion recurrent at the periodic
ity of said synchronizing signal and having mutually eX
clusive, equal durations together equal to the periodic
time of said synchronizing signal and applying said com
plex signals to respective switching devices each control
ling a signal channel connecting an individual one of said
input terminals to said output terminal in such a manner
that only the maximum positive-going excursion in said
complex signals cause said switching devices to allow
signals to pass,
References Cited in the ñle of this patent
Rotary-Head Switching in the Ampex Video Tape Re
corder, Journal of the SMPTE, April 1957, vol. 66,
o pages 184-188.
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