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United States Patent |
5,194,849
|
Rehder
|
March 16, 1993
|
Process for the deactivation of a resonance label and circuit
arrangement for the execution of the process
Abstract
A process and circut device for the deactivation and subsequent proof of a
resonance label which has a resonant circuit with a certain Q factor and a
certain frequency. The resonant circuit is energized with and disabled by
a deactivation energy during deactivation. During deactivation, time is
divided into a continuous alternating sequence of first and second time
periods which directly follow one another. A transmission antenna
transmits a deactivation energy during each of the first periods of time
in the form of a sequence of separate deactivation impulses to cause the
reosnant circuit of the resonance label to oscillate in a resonant mode.
The height and the width of each of the deactivation impulses and the
number of the deactivation impulses within the impulse sequence are such
that the impulse sequence delivers sufficient energy to deactivate the
resonance label. The transmission is stopped and the transmission antenna
is disabled for each of the second periods of time. A receiver is
activated at the beginning of each of the second periods of time. The
receiver receives decaying oscillations of a resonant label which is
present and which has not successfully been deactivated during the
preceding of the first time period.
Inventors:
|
Rehder; Jurgen (Bexbach-Hochen, DE)
|
Assignee:
|
Actron Entwicklungs AG (Rotkreuz, CH)
|
Appl. No.:
|
690692 |
Filed:
|
April 24, 1991 |
Foreign Application Priority Data
Intern'l Class: |
G08B 013/24 |
Field of Search: |
340/572
|
References Cited
U.S. Patent Documents
5023600 | Jun., 1991 | Szklany et al. | 340/572.
|
5027106 | Jun., 1991 | Lizzi et al. | 340/572.
|
5059951 | Oct., 1991 | Kaltner | 340/572.
|
Primary Examiner: Swann, III; Glen R.
Attorney, Agent or Firm: Tarolli, Sundheim & Covell
Claims
I claim:
1. A process for the deactivation and subsequent proof of a resonance label
which has a resonant circuit with a certain Q factor and a center
frequency, the resonant circuit being energized with and disabled by a
deactivation energy during said deactivation process, said process
comprising the steps of:
dividing time into a continuous alternating sequence of first and second
time periods which are directly following one another;
transmitting, by means of at least one transmission antenna, a deactivation
energy during each of the first periods of time in the form of a sequence
of separate deactivation impulses, the height and the width of each of the
deactivation impulses and the number of the deactivation impulses within
the impulse sequence being such that the impulse sequence delivers
sufficient energy to deactivate the resonance label for causing the
resonant circuit of the resonance label to oscillate in a resonant mode;
stopping said transmission and disabling the at least on transmission
antenna for each of said second periods of time; and
activating, at the beginning of each of the second periods of time,
receiving means for receiving decaying oscillations of a resonant label
which is present and which has not successfully been deactivated during
the preceding of the first time periods.
2. A process as set forth in claim 1, wherein the length of each of the
first periods of time is calculated from the Q factor and the center
frequency of the resonant circuit of the resonance label, the length of
each of the first periods being no more than 100 microseconds, the length
of each of the second periods of time being at least ten times the length
of the length of each of the first periods of time.
3. A process as set forth in claim 2, wherein the length of each of the
first periods of time is no more than 50 microseconds.
4. A process as set forth in claim 3, wherein the length of each of the
first periods of time is no more than 10 microseconds.
5. A process as set forth in claim 2, wherein the length of each of the
second periods of time is at least one hundred times the length of each of
the first periods of time.
6. A process as set forth in claim 5, wherein the length of each of the
second periods of time is at least one thousand times the length of each
of the first periods of time.
7. A process as set forth in claim 2, wherein the sequence of deactivation
impulses includes a maximum of 100 impulses.
8. A process as set forth in claim 7, wherein the sequence of deactivation
impulses includes about 50 impulses.
9. A process as set forth in claim 1, wherein the sequence of deactivation
impulses is periodical with certain impulse frequency, and the impulse
frequency is modulated within said sequence and/or during successive of
said first periods of time
10. A circuit device for the deactivation and subsequent proof of a
resonance label which has a resonant circuit with a certain Q factor and a
center frequency, the resonant circuit being energized with and disabled
by a deactivation energy, said circuit device comprising:
a clock generator for generating a clock frequency;
first timing means connected to said clock generator, said first timing
means deriving from said clock frequency a first periodical sequence of
impulses each of which has a length equal to a first time period;
second timing means connected to said first timing means, said second
timing means deriving from said first sequence of impulses a second
periodical sequence of impulses of the same periodicity, each of said
impulses of the second sequence having a length equal to one of a second
time period and adjoining a respective impulse of the first sequence, the
first and second time periods being in continuous alternating sequence
directly following each other;
an impulse generator for generating a continuous sequence of the
deactivation impulses with a certain impulse frequency;
transmitting means with at least one transmission antenna, said
transmitting means being connected to said impulse generator circuit via
first control means which are controlled by said first sequence of
impulses, means transmitting a deactivation energy during each of the
first periods of time in the form of a sequence of the deactivation
impulses and the number of the deactivation impulses within the impulse
sequence being such that the impulse sequence delivers sufficient energy
to deactivate the resonance label for causing the resonant circuit of the
resonance label to oscillate in a resonant mode;
receiving means with at least one receiving antenna and second control
means which are controlled by said second sequence of impulses, said
receiving means being activated at the beginning of each of the second
periods of time for receiving the decaying oscillations of a resonant
label which is present and which has not successfully been deactivated
during the preceding of the first time periods; and
disabling means which is connected to said at least one transmission
antenna and is controlled by said second sequence of impulses, said
disabling means stopping the transmission and disabling said at least one
transmission antenna for each of the second periods of time.
11. A circuit device as set forth in claim 10, wherein the impulse
frequency of said impulse generator is controlled by a frequency
modulation circuit, and said frequency modulation circuit is provided with
an adjustment device for the adjustment and change of the impulse
frequency.
12. A circuit device as set forth in claim 11, wherein said disabling means
includes a controllable attenuator which is in series with said at least
one transmission antenna.
13. A circuit device as set forth in claim 11, wherein said transmitting
means includes an amplifier and at least two transmission antennas which
are arranged vertical to each other and can be connected alternatingly to
said amplifier by means of a switching circuit.
14. A circuit device as set forth in claim 10, wherein said disabling means
includes a controllable attenuator which is in series with said at least
one transmission antenna.
15. A circuit device as set forth in claim 10, wherein said transmitting
means includes an amplifier and at least two transmission antennas which
are arranged vertical to each other and can be connected alternatingly to
said amplifier by means of a switching circuit.
16. A circuit device as set forth in claim 10, including at least one
antenna used as said at least one transmission antenna and as said at
least one receiving antenna, said transmitting means and said receiving
means each include an amplifier, said disabling means includes a switching
circuit which disconnects said at least one antenna from said transmission
amplifier and connects it to said receiving amplifier.
17. A circuit device as set forth in claim 10, wherein said circuit device
is connected with a bar-code scanner, on which at least one of said
transmission and/or receiving antennas is arranged.
18. A circuit device as set forth in claim 10, wherein said receiving means
includes an evaluation circuit which can be selectively switched by means
of an operational mode switch to either display the confirmation of a
successful deactivation of said resonance label or to an alarm display
mode for unsuccessful deactivations.
19. A circuit device as set forth in claim 10, wherein said circuit device
being positioned within an rf-tight housing with at least one opening as
receptacle for a material to be tested, said housing including a lid
movable to close the opening, movement of said lid operates a trigger
switch for staring said deactivation process.
20. A circuit device as set forth in claim 10, wherein said receiving means
includes elements for discriminating signals that are released by label
detection devices installed in the close vicinity and which produce a
suitable synchronization signal from said signals for a synchronization of
said deactivation impulse sequence transmission.
Description
BACKGROUND OF THE INVENTION
The invention concerns a process and a circuit arrangement for the
deactivation, and subsequent proof of deactivation, of a resonance label.
A process of this sort is already known from the EP-A-287 905 which has
also been applied successfully. However, it has to be considered that
contradicting demands exist in regard to the power emitted by the
deactivator. In order to be able to deactivate labels over the largest
possible distance and to avoid tight production tolerance for economical
reasons, the demand for the highest possible energy to be transferred onto
the label exists. On the other hand, legal barriers are set in specific
countries which set limits to the emitted power. These limits are simply
necessary because of the required compatibility with components of radio
frequency operated security devices. In this case the critical factors are
the peak values and the duration of the operating factor of the emitted
power.
SUMMARY OF THE INVENTION
The invention is thus based on the objective to transfer a maximum of
energy onto the resonance label with the shortest possible sending
duration and with low peak power. This objective is obtained by a process
for the deactivation and subsequent proof of a resonance label which has a
resonant circuit with a certain Q factor and a center frequency. The
process can be performed by a circuit device. The resonant circuit is
energized with and disabled by a deactivation energy during the
deactivation process. The process includes the step of dividing the time
into a continuous alternating sequence of first and second periods which
directly follow one another.
The process includes transmitting, by means of at least one transmission
antenna, a deactivation energy during each of the first periods of time in
the form of a sequence of separate deactivation impulses for causing the
resonant circuit of the resonance label to oscillate in a resonant mode.
The height and width of each of the deactivation impulses and the number
of the deactivation impulses within the impulse sequence being such that
the impulse sequence delivers sufficient energy to deactivate the
resonance label. The process includes stopping the transmission and
disabling the at least one transmission antenna for each of the second
periods of time. The process includes activating, at the beginning of each
of the second periods of time, receiving means for receiving the decaying
oscillations of a resonant label which is present and which has not
successfully been deactivated during a preceding one of the first time
periods.
The invention is based on measurements and experiments that show that the
equilibrium between emitted energy and the energy used in the label by
heat loss and radiation can already be obtained after relatively few
oscillations with a constant electromagnetic alternating field and with a
deactivation frequency that corresponds with the label. Each further
oscillation emitted from the deactivation antenna increases the
possibility of a deactivation of the resonance label only inconsiderably.
Because the process is executed with successive impulses within an impulse
group instead of with single impulses, as it is suggested in the
previously mentioned EP-A, each impulse represents an oscillation
stimulation for the resonant circuit determined by the label, in which the
energy which was only slowly released from the label is stored and built
up within the label. Each single impulse can thus be considerably weaker
than thus far assumed, if equally large ranges are considered. This means
that the possibility of interferences by other components is also reduced
considerably. Compared to conventional processes, this leads to
practically no increase in the total emitted energy despite the
utilization of one impulse group, which means from several impulses each,
because the single impulses are weaker.
According to a preferred example, the process is executed such that the
length of each of the first periods of time is calculated from the Q
factor and the center frequency of the resonant circuit of the resonance
label. In a preferred example, the length of each of the first periods is
no more than 100 microseconds, preferably no more than 50 microseconds,
and in particular no more than 10 microseconds. In a preferred example,
the length of each of the second periods is at least ten times, preferably
at least one hundred times, and in particular about one thousand times the
length of the first period. It is generally possible to select the
duration of the burst pauses, and the duration between two impulse groups
(bursts), in such a way that a certain amount of energy from the
previously emitted impulse group remains in the label if the same is not
yet deactivated and thus might contribute to the oscillation buildup.
According to a preferred example, the circuit device has a clock generator
for generating a clock frequency. The circuit arrangement has a first
timing means connected to the clock generator. The first timing means
derives from the clock frequency a first periodical sequence of impulses
each of which has a length equal to one of the first periods. The circuit
device has a second timing means connected to the first timing means. The
second timing means derives from the first sequence of impulses a second
periodical sequence of impulses of the same periodicity. Each of the
impulses of the second sequence having a length equal to one of the second
time periods and adjoining a respective impulse of the first sequence.
The circuit device has an impulse generator for generating a continuous
sequence of the deactivation impulses with a certain frequency. The
circuit device has a transmitting means with at least one transmission
antenna. The transmitting means is connected to the impulse generator
circuit via first control means which are controlled by the first sequence
of impulses. The circuit device includes receiving means with at least one
receiving antenna and second control means which is controlled by the
second sequence of impulses. The circuit device includes disabling means
which are connected to the at least one transmission antenna and is
controlled by the second sequence impulses.
BRIEF DESCRIPTION OF THE DRAWINGS
Further details of the invention result from the following description of
the examples that are schematically represented in the drawings.
FIG. 1: a first example of a circuit arrangement according to the
invention, in particular for battery operation;
FIG. 2: an alternative with a simplified circuit; and
FIG. 3: a modified example with at least two transmission antennas.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
A central clock generator 1, for example with a clock frequency of between
20 and 30 Hz, preferably 25 Hz, is supplied by a power supply unit 15
which can include one or more batteries, as this is symbolically shown;
however, it can also be provided with circuit connectors 16 and, if so
desired, can be switched between either one of the two power sources.
The clock generator 1 can be provided with a synchronization coupling 17 in
order to be able to be synchronized with other devices. The frequency of
the clock generator determines the number of transmissions (number of the
emitted impulse groups or bursts per time unit) of the deactivation
circuit. For this purpose a sequence of short strobe impulses is produced
from the edges of the rectangular output voltage of the clock generator 1
by a stage 2.
It should also be mentioned that it would generally be possible to utilize
a clock generator 1 with different forms of signals than rectangular
impulses, but then a subsequently switched impulse forming stage would
have to be inserted because only the most defined edges are advantageous
for the production of the strobe impulses in the stage 2. This stage 2
represents some sort of time function element that determines the burst
duration by the duration of the rectangular signals produced by it. It
can, for example, be constructed as a flip-flop that reacts to the
ascending edges of the rectangular signal produced by the clock generator
1.
Because the energy transmitted to the labels can only be effectively
utilized during limited durations, the duration of the strobe impulses has
to be limited correspondingly. The maximum number of impulses per impulse
group will in general be determined by the Q-factor of the kind of
resonance labels utilized. A label with a high Q-factor will most of the
time necessitate more impulses until the equilibrium between the received
and emitted power is obtained than a label with a lower Q-factor. It
always should be remembered that the Q-factor, as already described in the
EP-A-285 559, depends on one hand on the quality of the dielectric of the
label and on the other hand on the size of the space free of conductive
coating within the inductor winding. It is especially beneficial if the
number of impulses per impulse group is calculated from Q/2, which means
it corresponds with half the Q-factor. This means that, for example, a
label with the factor Q=100 necessitates about 50 impulses which, for
example, corresponds with a duration of the strobe impulses of about 6
microseconds with an impulse frequency of 8 MHz. This is the reason why
the duration of the strobe impulses should amount to no more than 100
microseconds, but will lie considerably below this value in most cases,
for example at about 50 microseconds. Practical experiences have shown
that durations of 10 microseconds can be sufficient. These ratios can vary
depending on the construction of the labels and the local conditions, but
usable results were already obtained with durations of only about 5
microseconds (.+-.1 microsecond). It was even possible to obtain durations
of only 1 microsecond.
The strobe impulses released by the time function element 2 reach the input
of a gate circuit (AND-gate) 3, whose other input is connected with an
impulse sequence generator 4 that preferably produces a sequence of
rectangular impulses. This gate 3 is opened by the strobe impulses of the
time function element 2 and allows the penetration of a group of impulses
that were released by the generator 4 during the corresponding duration
(the burst duration). The strobe time is selected in correspondence with
the previously described text in order to allow the penetration of the
desired number of impulses.
This clearly shows that the stages 1 through 4 together represent the
impulse generator circuit for the emission of impulse groups or bursts.
They can, if so desired, be replaced by other circuits, for example by an
HF-start-stop generator that is activated by a time function element and
thus switches itself off after each start and after emission of the
predetermined number of impulses. The initially described solution is
preferred because such a generator generally necessitates a certain
response time.
It is already known that the resonance labels are subject to certain
production tolerances, which should not be set too strictly for production
purposes. Analog to this it is also possible that the natural frequency
and/or resonance frequency of such labels can be subject to certain
fluctuations. It is thus advantageous if the impulse sequence generator 4
either contains an impulse sequence frequency modulator within itself or,
as shown, is connected with an external modulator 14. This stage 14 can be
constructed in different forms and can also have different functions. An
adjustment of the frequency spectrum is desired because an adaptation to
the utilized labels is very advantageous. In this case, the stage 14 can
be provided with a device 18 that allows either continuous adjustment or a
change-over.
For the purpose of modulation of the impulse sequence frequency, two other
possibilities are applicable: the modulation can be executed either within
a single impulse group or from burst to burst. Because the burst duration
is relatively short, the first variation will only show conditional
success if it is not coupled with at least the second variation. In the
most simple structural solution, a modulator is constructed as a ramp
generator which impresses a continuous displacement of the impulse
sequence frequency on the generator 4, in which the displacement will show
its effect within each impulse group, as well as from impulse group to
impulse group. However, if the modulator 14 is controlled by the outputs
of an amplifier stage 5 and is thus indirectly controlled by the strobe
impulses of the time stage 2, then no displacement of the frequency occurs
during the burst pauses between the single impulse groups, but always
occurs during a strobe impulse, in which the length of the ramp
corresponds with a multiple of the duration of the strobe impulse and is
thus only completed after several strobe impulses.
The amplifier 5 has the role of a driving circuit for a high-level stage
(power stage) 6 that obtains its power supply by a voltage transformer 7.
This voltage transformer is, just like the HF-oscillator 4, shown as being
connected to the supply stage 15 and can be provided with a separate power
supply if the same is obtained by batteries. The signal is subsequently
conveyed from the power stage 6 to the transmission antenna C, L1.
Because of the relatively low total energy consumption it is easily
possible to construct the deactivation circuit as battery operated device.
In any case it is advantageous to connect the circuit with a conventional
bar-code-scanner 19 or to attach at least one of the two antennas C, L1
and/or L2 shown on the housing of this scanner 19. The scanner 19 can be
constructed differently, however it is advantageous if a flatbed scanner
or a vertical scanner, as they are utilized in cash registers, is applied.
The advantage of such a measure is clear: during the reading of the bar
code, which is most of the time attached to a resonance label, by the
scanner 19 an automatic and simultaneous deactivation of the label is
executed. The deactivation circuit can be constructed much simpler because
of the smaller dimensions (=lower deactivation output). With flatbed
scanners the antenna is, for example, simply mounted onto the scanner as
an accessory or with vertical scanners is simply assembled in front of the
scanner. This can even result in an especially high deactivation rate, if
the scanner is held immediately onto the label. This can even further
reduce the necessary deactivation energy.
The scanner 19 can be connected to the shown circuit arrangement by means
of a plug jack 20 and a coupling 21, in which the plug jack 20 can close
the circuit for a change-over 22 that can selectively switch the power
supply from battery operation to the main power supply circuit. This
change-over also allows the switching to battery operation if so desired.
FIG. 1 shows that a second time function element 9, which the output of the
time function element 2, in which this flipcan, flop produces strobe
impulses with a considerably longer impulse duration compared to the
impulse duration of the strobe impulses produced by the time function
element 2. This time function element 9 switches on the reception circuit
during the burst pauses. For this purpose the time function element 9 is
triggered by the descending edge of the strobe impulse from the stage 2.
The reception circuit detects a subsequently oscillating (and thus
apparently not yet deactivated) label. Such a signal is received by the
already mentioned reception antenna L2, which is switched before a
limitation stage 10 in order to prevent a saturation and destruction of
that part of the reception. As soon as an HF-amplifier 11 is released by
the time function element 9, the received signal can be correspondingly
amplified and conveyed to an evaluation stage 12 which, as symbolically
shown, can also trigger optical and/or acoustical signal devices 23, 24.
It might also be desired to trigger the signals devices 23, 24 for
different purposes. In some locations it might be preferred if the
corresponding signal device 23 or 24 respectively is only triggered if a
deactivation has not been executed. This will also be the normal scenario.
Sometimes it might also be desired that the successfully executed
deactivation is confirmed by the corresponding signal device 23 and/or 24
by activation of the same. If the latter is the case, only a selector
switch 25 has to be connected to the circuit shown.
By different logical interactions it is also possible to activate other
operational modes of the signal devices 23, 24, for example by interaction
of the information "label registered," "label produces subsiding echo"
(not deactivated), "label echo does not occur abruptly" (deactivated). The
change-over 25 can be formed by a switch that can be adjusted to several
different positions instead of by one simple switch, as it is shown.
FIG. 1 also shows that the time function element 9 does not only open and
close a time window while the reception circuit L2, 10-12, 23-25 is
activated, but that this time window signal also reaches a circuit stage
S1 over an amplifier 8 (for the adaptation of the impedance).
An attenuator resistor circuit R1 is switched into the antenna circuit C,
L1 by means of this circuit stage S1 which is preferably formed by an
electronic switch. The attenuator resistor circuit R1 can be formed by a
single attenuator resistor, as it is shown in our example, or by several
elements. The interfering influence of the resonant antenna circuit C, L1
on the receptor circuit is largely eliminated by this attenuator resistor
circuit R1 and thus simplifies the subsequent detection of eventual label
echoes by the reception antenna L2. During the duration of the strobe
impulses, which means while the bursts are emitted and increased power is
fed into the antenna C, L1, the switch S1 is closed and the attenuator
resistor circuit R1 is bypassed.
In order to avoid an influence of this label deactivation on a label
detection system operating in the close vicinity, the clock generator 1
can be synchronized with this particular detection system. This can, for
example, be obtained by means of a cable and the connector 17; on the
other hand the necessary synchronization signal can also be obtained in a
wireless manner from the reception circuit. For this purpose, the same is
provided with elements 26 (FIG. 1) which are able to discriminate the
signals received from the label detection system and to produce a suitable
synchronization signal from the same for the synchronization of the
impulse sequence transmission. It should also be mentioned that it might
not only be desired to synchronize the clock generator 1 with other
components by the connection 17, but to also divert a synchronization
signal from the circuit in order to determine when a burst pause occurs.
This can be obtained by a synchronization output 17'.
In the example according to FIG. 2 the same elements that have the same
function also carry the same reference symbols as in FIG. 1. In this case
some elements of the illustration in FIG. 1 are missing, because they
either are actually not present or are present but not shown. In any case
it is understood that the single characteristics of the different examples
can be replaced amongst each other and/or combined with each other.
This again primarily concerns a battery operated device, although a power
circuit operated device is also possible. This can also be seen in
connection with a bar-code-scanner 19. In order to simplify the circuit
and to be able to attach the antenna C, L in a more simple manner on the
housing of the scanner 19, only one single antenna C, L is provided which
is alternately operated as transmission and reception antenna.
For this purpose, the output of the power stage 6 and the input of the
limitation stage 10 is connected with a controlled change-over stage S1'
that alternately connects the antenna C, L with the output of the power
stage 6 and/or the input of the limitation stage 10. The control of this
change-over stage S1, is executed by the time window signal of the time
function element 9 and the amplifier 8, similar to the circuit stage S1 in
FIG. 1. This means a more space-saving form of construction and represents
an advantageous form of construction, compared to conventional circuits in
which such a change-over possibility is rather unlikely. The attenuator
resistor R1 can be switched as natural resistor of the limitation stage 10
and can be bypassed by the circuit stage S1. It could also be switched off
in a different manner than by bypassing.
If a label assumes a difficult position relative to the transmission
antenna, as for example exactly vertical to the antenna, then it can
practically receive no energy from the same. In order to avoid this, it is
advantageous if a number of transmission antennas are provided, which
means at least two. In the case of two transmission antennas C1', L1' and
C", L1" shown in FIG. 3 it is advantageous (because of the occurrence
mentioned in the beginning of this paragraph) if these antennas are
arranged vertically to each other. If more than two antennas are provided,
which will generally not be necessary, they can be arranged in
corresponding angles to each other.
In this case it is of the utmost importance that the output signals of the
power stage 6 are distributed on the transmission antennas C', L1' and C",
L1", which in turn is obtained by a change-over stage S1, that is assigned
to the antennas and has the function of a multiplex stage if several
antennas are provided. However, this multiplex stage S1" is not controlled
by the time function element 9 like the other antennas that are assigned
to the circuit stage S1 and S1, but by a frequency divider 13 that again
divides the strobe impulses from the time function element 2 in order to
convey the impulses of an impulse group to the antenna C1', L1' in half of
the time and to the antenna C", L1" in the other half of the time. In
correspondence with this, the strobe impulses of the stage 2 will be
longer than in the cases described in FIGS. 1 and 2.
Because in this case another separate reception antenna is used, it is
suggested that absorptive attenuators R1' and R1" should be provided in
the antenna circuits C', L1' and C", L1" and that the same can be bypassed
for the transmission mode by the circuit stages S1a and S1b. Because the
transmission antennas are only effective in succession, it would also be
possible to not address them by the time function element 9, but to also
synchronize them with the frequency divider 13, but this effort is not
necessary in most cases. It would also be possible to address the two
antennas circuits C', L1' and C", L1" in a parallel manner from the output
of the power stage instead of after each other; however, this would lead
to a separation of the energy which in turn can lead to problems and which
is the reason why the shown arrangement of a multiplex stage S1" is
preferred. It is also understood that such an arrangement of several
transmission antennas can be realized advantageously independent from the
fact if the process is executed with the described burst signals or not
and if the described attenuator arrangement R1, R1' or R1" that can be
switched off is present or not. On the other hand, such a multiple antenna
arrangement can also be applied advantageously in the examples according
to FIG. 1 or 2.
Especially with several antennas it can be advantageous if the entire
arrangement is assembled within a housing 26 from which only the signal
devices 24 and 23 lead towards the outside. Such a housing 26 is
constructed as an HF-tight housing that is provided with at least one
entry opening (if desired, also with an exit opening according to luggage
x-ray apparatuses in airports) that can be closed by a lid, in which the
product for the activation of the label is inserted into the housing or is
conveyed through the same. In this case the construction can be chosen in
such a way that a deactivation switch is closed when the housing lid is
shut, by means of which a deactivation impulse, or, as in the case of the
above described invention, an impulse group (burst) is released.
Several modifications are possible within the general idea of the
invention; it is thus understood that the stage 13 in FIG. 3 represents a
synchronization element which can be replaced by any other synchronization
circuit, if so desired.
An additional time function element that is controlled by the stage 2 and
is synchronized with the same, could be provided for the control of the
change-over device S1' in FIG. 2, but the utilization of the time function
element 9 that is necessary anyhow and that produces the burst pauses is
considerably simpler.
Further modifications can result from the housing 26 and its lid that
activates the deactivation switch: it is not absolutely necessary that the
deactivation is triggered by such a switch; it is possible to run the
deactivation signal within the housing 26 in a continuous mode, especially
if the housing is constructed as conveyance housing. On the other hand, in
most cases such a trigger switch will be desired, even if there is no
housing 26 provided. Such a trigger switch (although not shown) can be
arranged on different locations, for example on the power supply unit 15
itself, in order to be able to switch the same on and off centrally and to
switch off all circuit elements. It would also be possible to run at least
part of the circuit in the mode of a standby operation (for example the
clock generator 1 or the impulse sequence generator 4) and to only switch
off the remaining parts or to arrange the trigger switch between the power
supply unit 15 and the clock generator 1, in which case an opening of the
gate circuit 3 is impossible. A further possibility consists of the fact
to arrange the trigger switch between the oscillator 4 and the AND-gate 3,
in which the oscillator 4 can run freely and is only switched into the
circuit if this is desired. In an alternate version it would also be
possible to arrange the trigger switch between the voltage transformer 7
and the high-level stage 6. The antenna provides only weak signals that
energize the resonance of the label only if the trigger switch is not
activated, in order to detect a theft attempt. On the other hand it
provides the deactivation impulses. In this case it is advantageous to
arrange a connection with an operational mode switch that corresponds with
the switch 25, yet shows several different positions, for the evaluation
circuit 12, in order to release a "theft detection signal" if the
transmission antenna only releases weak label detection signals, but on
the other hand only differentiates between "label deactivated" or "label
not deactivated."
As far as the time function element 2 is concerned it can be constructed as
a multivibrator, in particular an unstable multivibrator. However, it can
preferably contain a counter, that counts the received clock impulses and
forms the corresponding strobe impulses from the same.
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