JPH03189717A - Position detector and its position pointer - Google Patents

Abstract

PURPOSE:To transmit a large quantity of switch information by transmitting the radio waves via a tablet, changing the phase angle or the frequency of a tuning circuit via a position pointing device in the prescribed timing, and detecting the phase angle or the frequency of the radio wave at the tablet side. CONSTITUTION:The prescribed timing information is extracted out of the voltage induced at a tuning circuit of a position pointing device B with the electric wave received from a tablet A. The frequency or the phase angle of the tuning circuit is changed in accordance with the operation of a switch, etc., in the specific timing set based on the prescribed timing information. In this case, however, the change of the frequency or the phase angle of a received signal is detected via the tablet A in the specific timing. Thus the operation of the device B is identified to the switch of the device B, etc. Thus it is possible to transmit a large quantity of switch information to the tablet A from the device B in a short time and with no mistake.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement of a position detection device using radio waves and a position indicator thereof.

(Prior Art) Prior to filing this application, the applicant filed Japanese Patent Application No. 61-213970.
No. 63-70326 (hereinafter referred to as the prior application), a position is disclosed in which radio waves are transmitted and received between a tablet and a position indicator to determine the coordinate values of a position designated by the position indicator. A detection device was proposed.

To briefly explain the content of the earlier application, the tablet is equipped with a large number of loop coils arranged in parallel in the position detection direction.
An alternating current signal of a predetermined frequency is applied to the - loop coil to transmit radio waves, and the radio waves excite a tuned circuit built in the position indicator. At this time, radio waves generated by the tuned circuit are received by the loop coil and generate an induced voltage. By sequentially switching and repeating this for each loop coil, a voltage value depending on the distance to the position indicator is obtained for each loop coil, and from these, the coordinate values of the position specified by the position indicator are determined.

By the way, in this type of position detection device, in order to specify the position to be actually input, it is necessary to transmit some information from the position indicator to the tablet.

In the prior application, by connecting another capacitor (or coil) to the coil and capacitor constituting the tuning circuit via a switch, the tuning frequency is slightly changed depending on the operation of the switch, and this tuning A slight change in frequency was detected as a change in phase angle on the tablet side, and was used as the information described above.

FIG. 2 shows an example of the above-described position indicator, in which a coil 1 and a capacitor 2 are connected in series to form a tuned circuit with a predetermined frequency. Also, capacitor 3.4
．． 5.6 have different capacitance values, and switch 7
．． 8, 9, and 10 in parallel to the capacitor 2. Therefore, the tuning frequency changes by a different frequency depending on the operated switch, and the tablet side can identify the operated switch based on the phase angle of the received signal at that time.

FIG. 3 shows another example of the position indicator, in which the coil 11
and capacitor 12 are connected in series with each other to form a tuned circuit of a predetermined frequency. Further, the capacitor 13 is connected in parallel to the capacitor 12 via an analog switch 14. The code generator 15 includes a number of switches 16-1, 16-2 .・・・・・・16 ・A predetermined bit, corresponding to the state of the selection input terminal to which -n is connected,
For example, an 8-bit binary code is output and the analog switch 14 is turned on and off. Therefore, the 2 corresponding to the operation switch
The tuning frequency will change to a predetermined frequency and a slightly different frequency depending on the base code, and the tablet will change the pattern of the phase angle change of the received signal at that time into two.
The operated switch can be identified by converting it into a decimal code.

(Problem to be Solved by the Invention) However, since the phase angle detected by the tablet changes somewhat due to changes in ambient temperature, etc., in the case of the circuit shown in Fig. 2, the phase angle when identifying the operation of each switch is It is necessary to have a certain range of width, and for this reason, it is not possible to increase the number of distinguishable switches very much.

In addition, in the case of the circuit shown in FIG. 3, it is possible to provide the number of switches according to the number of bits of the code generator 15, but the code generator 15 operates at a unique timing unrelated to the tablet, and the analog switch 14 intermittently, there was a drawback that it took time for the tablet to convert the pattern of phase angle changes into a binary code.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to realize a position detection device and its position indicator that can transmit a large amount of switch information from a position indicator to a tablet without error and in a short time.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a position indicator having at least a tuned circuit, and a coordinate value of a specified position by alternately transmitting and receiving radio waves to and from the position indicator. In a position detection device consisting of a tablet that seeks The tablet is provided with means for detecting the phase angle or frequency of the radio waves generated from the tuned circuit, and means for extracting predetermined timing information from the induced voltage generated in the tuned circuit, and means for detecting a specific timing information based on the predetermined timing information. A position detection device in which a position indicator is provided with a means for changing the phase angle or frequency of a tuned circuit based on the operation of a switch or the like, a tuned circuit, and predetermined timing information from an induced voltage generated in the tuned circuit. and means for changing the phase angle or frequency of a tuned circuit based on the operation of a switch or the like at a specific timing based on the predetermined timing information.

(Function) According to the present invention, predetermined timing information is extracted from the induced voltage generated in the tuned circuit of the position indicator by radio waves transmitted from the tablet, and the frequency is determined at a specific timing based on the predetermined timing information. Alternatively, the phase angle is changed according to the operation of a switch, etc., but in this case, the tablet detects the change in the frequency or phase angle of the received signal at the specific timing, and from this, the operation of the position indicator on the switch, etc. is identified. .

(Embodiment) FIG. 1 shows a first embodiment of a position detection device and a position indicator thereof according to the present invention. In the figure, 21 is a sensing section, 22
23 is a selection circuit, 23 is a transmission/reception switching circuit, 24 is an oscillator, 25
2 is a voltage detection circuit, 26 is a phase comparator, and 27 is a processing device, which constitute the tablet A. Further, 31 is a coil, 32 is a capacitor, 33 is an envelope detector (hereinafter simply referred to as a detector), 34 is a waveform shaper, 35 is a reset circuit, 36 is a counter, 37 is an AND gate, 3
8 is an analog switch, CI, C2,...Cn
are capacitors, Sl, S2. ...Sn is a switch, and these constitute the position indicator B.

The sense section 21 is constructed by overlapping a large number of loop coils arranged in parallel in the X direction at predetermined intervals and a large number of loop coils arranged in parallel in the Y direction at predetermined intervals. The selection circuit 22
One loop coil is selected from a large number of loop coils in the direction and the Y direction, and operates based on selection information from the processing device 27. The transmission/reception switching circuit 23 is an oscillator 24 for the negative loop coil in the selected X direction or Y direction.
and the voltage detection circuit 25, and operate based on a switching signal from the processing device 27. The oscillator 24 generates a reference clock of a predetermined frequency fo, and supplies this to the transmission/reception switching circuit 23 via the phase comparator 26, the processing device 27, and a low-pass filter and drive circuit (not shown).

The voltage detection circuit 25 includes an amplifier, a bandpass filter having the frequency fo as a passband, a detector, and a low-pass filter, and outputs a DC signal having a voltage value corresponding to the energy of the frequency fo acid component in the received signal. The phase comparator 26 is composed of a phase detector and a low-pass filter, and receives the reference clock of frequency fo and the received signal passed through the bandpass filter from the voltage detection circuit 25, and calculates the phase angle between the received signal and the reference clock, that is, the transmitted signal. A DC signal having a voltage value corresponding to the difference between the two is output.

The processing device 27 is composed of a well-known microprocessor or the like, and creates a transmission/reception switching signal from the reference clock of the frequency fo and supplies it to the transmission/reception switching circuit 23, and also controls the selection circuit 22 according to the flowchart described later to output the signal to the sensing section 21. It also converts the output voltages of the voltage detection circuit 25 and phase comparator 26 into analog/digital (A/D), executes predetermined arithmetic processing, and obtains the coordinate values of the specified position by the position indicator B. and the operated switch.

The coil 31 and the capacitor 32 are connected in series and constitute a tuned circuit with a frequency fO. The detector 33 is for extracting the repetitive timing component of transmission and reception by the tablet A from the signal generated in the tuning circuit. The waveform shaper 34 extracts a signal having a predetermined voltage value VT or more from the output signal of the wave detector 33, shapes the waveform into a pulse signal, and sends it to the reset circuit 35 and counter 36.

The reset circuit 35 is composed of a retriggerable monostable multivibrator that outputs a signal with a pulse width approximately twice the repeat timing of transmission and reception of the tablet A described above, and is triggered and operated at the rising edge of the pulse signal. The counter 36 is used to determine the initial mode, position detection mode, and switch identification mode of the tablet A, which will be described later, from the pulse signal, and divides the pulse signal into 1/8 and 1/32 and outputs it, and resets the counter 36. It is reset by the output of the circuit 35.

The AND gate 37 creates a specific timing in the switch identification mode, in this case, a timing for turning on the analog switch 38, from the output of the counter 36.

One end of the analog switch 38 is connected to one end of the capacitor 32, and the other end is commonly connected to one end of the capacitors C1 to Cn. The other ends of the capacitors C1 to Cn are connected to ground, that is, to the other end of the capacitor 32 via switches 81 to Sn, respectively, and therefore, while the analog switch 38 is on, the switch S operated at that time
One of the capacitors C1 to Cn corresponding to C1 to Sn is connected in parallel with the capacitor 32.

The values of capacitors C1 to Cn change the tuning frequency of the above-mentioned tuning circuit by a small preset value, and change the phase angle detected by tablet A. Note that the waveform shaper 34, reset circuit 35, and
The counter 36, AND gate 37, and analog switch 38 are driven by a battery (not shown).

FIG. 4 is a flowchart of processing in the processing device 27, and FIG. 5 is a signal waveform diagram of each part in the tablet position detection mode and switch identification mode, and the operation will be explained below according to these.

First, the processing device 27 of the tablet A
Sequentially select all the loop coils in the direction and Y direction, repeat the transmission and reception of radio waves for each loop coil, detect the strength of the received signal, and check whether the position indicator B is within the effective reading area of the sense unit 21. If it is within the area A, it is detected which loop coil among the large number of loop coils in the X and Y directions is closest to the position indicator B (initial mode).

Specifically, first, information for selecting the negative loop coil of the sensing section 21 is sent to the selection circuit 22, and a signal for selecting the transmitting side is sent to the transmission/reception switching circuit 23.
A sine wave signal of frequency fo based on the reference clock of the oscillator 24 is supplied to the - loop coil to generate a radio wave of frequency fo. At this time, when the position indicator B is placed on the sensing section 21, the radio wave excites a tuned circuit consisting of a coil 31 and a capacitor 32, and the frequency f
Generates an induced voltage of O.

When the processing device 27 sends a signal for selecting the transmitting side to the transmission/reception switching circuit 23 for a certain period of time, it sends a signal for selecting the receiving side, and eliminates the radio waves generated by the loop coil. At this time, the induced voltage generated in the tuned circuit of the position indicator B gradually attenuates according to its loss and emits a radio wave with a frequency fO, but this radio wave reversely excites the loop coil mentioned above. Generates an induced voltage.

After the processing device 27 sends a signal for selecting the receiving side to the transmission/reception switching circuit 23 for a certain period of time similar to the above, it sends out a signal again for selecting the sending side, and thereafter transmits and receives radio waves in the same manner as described above.
Repeat for a total of 4 loop coils. The processing device 27 changes the information sent to the selection circuit 22 to switch the loop coil to be selected, and thereafter transmits and receives radio waves in the same manner as described above for all the loop coils in the X direction and the Y direction. The induced voltage generated in the loop coil of the sensing section 21 during the reception period is averaged by the bandpass filter of the voltage detection circuit 25, and further detected, converted to a DC voltage, and sent to the processing device 27. Since the voltage value of the DC voltage is a value that depends on the distance between the position indicator B and the loop coil, it is determined whether the maximum values in the X direction and the Y direction are greater than or equal to a predetermined threshold value set in advance. By this, it is determined whether or not the position indicator B is within the effective reading area of the sensing unit 21, and if it is determined that it is within the area, the maximum values in the X and Y directions at that time are obtained. The loop coils are stored as the loop coils in the X and Y directions closest to the position indicator B, and the next position detection mode is activated. Note that if it is determined that the position indicator B does not exist within the area, the initial mode is repeated.

In the position detection mode, the processing device 27 selects information to sequentially select a predetermined number of loop coils, in this case eight loop coils, centering on the memorized loop coil in the X and Y directions from which the maximum induced voltage was obtained. The signal is sent to the circuit 22 to transmit and receive radio waves in the same manner as described above. At this time, it is determined whether the maximum value of the obtained induced voltage is greater than or equal to the predetermined threshold,
If it is below the threshold, the process returns to the initial mode described above. In addition, if it is above the threshold value, the X direction and Y direction are
Find the coordinates of a specified position in a direction. Note that the specific method of calculating the coordinate values is the same as that of the previous application described above, so it will not be described in detail.

In the position detection mode described above, as shown in Fig. 5, radio waves are transmitted 4 times to each of the 8 loop coils in the X direction and the Y direction, a total of 64 times (signal a).
However, due to the difference in distance between the position indicator B and the loop coil, induced voltages of different levels are generated at both ends of the capacitor 32, as shown in the signal diagram. Therefore, the detection output C exceeds the voltage value v1H only when radio waves are transmitted from the loop coil closest to the position indicator B and the loop coils on both sides thereof. As a result, analog switch 3
The drive signal 8 never becomes high level, and the analog switch 38 does not operate in the position detection mode (the same goes for the initial mode).

When the position detection mode ends, the processing device 27 activates the switch identification mode. In the switch identification mode, the processing device 27 sends information for selecting the X-direction (or Y-direction) loop coil from which the maximum induced voltage was obtained in the position detection mode to the selection circuit 22, and also Transmission and reception are repeated a predetermined number of times, in this case 24 times.

In this case, the selected loop coil is position indicator B.
, a constant high-level induced voltage is generated at both ends of the capacitor 32 for all 24 transmissions and receptions of radio waves.

Therefore, the detection output C also exceeds the voltage value vTH for all 24 transmissions and receptions of radio waves, and 24 pulse signals corresponding to all 24 transmissions and receptions of radio waves are obtained as the waveform shaping output d. As a result, signals are obtained at the two outputs f and g of the counter 36, and the output of the AND gate 37 is at a high level only during the period corresponding to the period from the 21st to the 24th time of transmission and reception of radio waves. analog switch 38
turns on. When the analog switch 38 is turned on,
As mentioned above, the switches 81 to Sn operated at that time
Capacitors C1 to Cn corresponding to the above are connected in parallel with the capacitor 32, and the tuning frequency thereof changes slightly.

Of the phase comparison output j obtained from the phase comparator 26, the processing device 27 of the tablet A calculates the value (detected phase) obtained during the radio wave transmission and reception period from the 21st to the 24th time described above, and Other than that, for example, the value (reference phase) obtained during the transmission and reception period of radio waves from the 17th time to the 20th time is read, and the difference therebetween is calculated. The reference phase corresponds to the tuning frequency when the tuning circuit of the position indicator B consists of only the coil 31 and the capacitor 32, and the detection phase corresponds to the tuning frequency when the tuning circuit of the position indicator B consists of only the coil 31 and the capacitor 32. Since it corresponds to the tuning frequency of the connected tuning circuit, the difference corresponds only to the capacitance value of the connected capacitor.

Therefore, if the phase difference when each switch 81-Sn is operated and the capacitors C1-Cn are connected is calculated and stored in advance, the operated switch can be identified from the obtained phase difference.

Note that the obtained coordinate values of the designated position and switch information are transferred to a host computer (not shown), etc., and used for various processing.

According to the embodiment described above, it is possible to obtain a phase angle difference that depends only on the capacitance value of the capacitor corresponding to the operated switch, so it is possible to provide a larger number of capacitors, that is, a larger number of switches than before. Further, instead of providing a large number of switches and capacitors, it is also possible to provide a capacitor whose capacitance value changes continuously according to the operation, and to determine the amount of operation.

FIG. 6 shows a second embodiment of the present invention, in which information corresponding to operation switches is transmitted in an 8-bit binary code.

That is, in the figure, 28 is a processing device, which is the same as the processing device 27 of the first embodiment except that the operation in the switch identification mode is slightly different. The processing device 28, a sense section 21 similar to the above, a selection circuit 22, a transmission/reception switching circuit 23,
The tablet C is composed of the oscillator 24, the voltage detection circuit 25, and the phase comparator 26.

Further, 39 is a counter, 40 is a flip-flop (FF
), 41 is a code generator, 42 is a parallel-to-serial (P-8) conversion circuit, 43 is a capacitor, and the same coil 31, capacitor 32, and detector 33 as described above.
, the waveform shaper 34, the reset circuit 35, and the analog switch 38 constitute a position indicator.

The counter 39 is for determining the initial mode, position detection mode, and switch identification mode of the tablet C from the output pulse of the waveform shaper 34, and divides the pulse signal into 1/4 and 1/32 and resets it. It is reset by the output of the circuit 35. The FF 40 creates a signal that limits the period during which the P-S conversion circuit 42 is operated in the switch identification mode from the 1/32 frequency-divided output of the counter 39. Also, the 1/4 frequency divided output of the counter 39 is P
-8 Input as the operation clock of the conversion circuit. The code generator 41 generates an 8-bit binary code according to the operated switch among the directly attached switches 81 to Sn, and a specific example thereof is shown in FIG.

The P-8 conversion circuit 42 converts the binary code from the code generator 41 one bit at a time to the analog switch 38 every time the fall of the 1/4 frequency divided output of the counter 39 is input while the output of the FF 40 is at a high level. send and control on/off. The capacitor 43 is connected in parallel to the capacitor 32 via the analog switch 38. Therefore, the tuning frequency changes slightly between the on period and the off period of the analog switch 38, and the phase detected by the tablet C changes slightly. The angle will also change.

FIG. 8 is a flowchart of processing in the processing device 28, and FIG. 9 is a signal waveform diagram of each part. The operation will be described below, but since the initial mode and position detection mode are the same as those in the first embodiment, their explanation will be omitted.

In the switch identification mode, the processing device 28 sends information for selecting the X-direction (or Y-direction) loop coil for which the maximum induced voltage was obtained in the position detection mode to the selection circuit 22, and also Transmission and reception are repeated a predetermined number of times, in this case 48 times (signal k).

In this case, an induced voltage g of a constant large level is generated across the capacitor 32 for all 48 transmissions and receptions of radio waves. Therefore, the detection output m also has a voltage value V, 1 or more for all 48 times of radio wave transmission and reception, and the waveform shaping output n has a voltage value of 4 or more corresponding to all 48 times of radio wave transmission and reception.
Eight pulse signals are obtained. As a result, counter 39
A signal is obtained at the output p of FF40 and the output r of FF40, and P-8
The conversion circuit 42 receives an operation clock synchronized with the end of the 16th, 20th, 24th, 28th, 32nd, 36th, 40th, and 44th transmission/reception of radio waves.

As described above, the P-8 conversion circuit 42 outputs the 8-bit binary code supplied from the code generator 41 one bit at a time each time the operating clock is input, so that the P-8 conversion circuit 42 outputs the 8-bit binary code supplied from the code generator 41 one bit at a time. The 1st bit is used until the 20th bite, from the 21st bit to the 24th bit, from the 25th bit to the 28th bit, from the 29th bit to the 32nd bit, and from the 29th bit to the 32nd bit. From the 33rd mouth to the 36th mouth, from the 37th mouth to the 4th mouth
From the 0th opening, from the 41st opening to the 44th opening, and from the 45th opening to the 48th opening are the 2nd and 3rd openings, respectively. Fourth
．． Fifth. 6th. 7th. The eighth bit is output as signal S. The analog switch 38 is controlled on and off according to the level of the signal S, and when it is on, the capacitor 43 is connected across the capacitor 32, and its tuning frequency changes slightly.

The processing device 28 of the tablet C processes the phase comparison output U obtained from the phase comparator 26 from the 17th to the 20th, from the 21st to the 24th, and so on.
...The values obtained during the radio wave transmission/reception period from the 45th to the 48th are converted into binary codes. in particular,
The capacitance value of the tuned circuit of position indicator C is analog switch 3.
8 is on, and the tuning frequency becomes lower, that is, the phase angle is delayed, so among the values obtained during the radio wave transmission and reception period described above, the value corresponding to the more delayed phase angle is set to bit "1". , and set the other values as bit “0” to 8
Convert to bit binary code. Also, read the value obtained during the radio wave transmission and reception period from the 13th to the 16th intercostals other than the above, and compare it with the values for each period described above. If the values are the same, the bit "0" is read. '', and if different, the bit may be set to ``1'' and converted to an 8-bit binary code.

The 8-bit binary code obtained in this way matches the binary code generated by the code generator 41, so if you memorize the codes generated when the switches 81 to Sn are operated in advance, you can obtain a profit. The operated switch can be identified from the binary code given.

According to the embodiment, since the binary code can be transmitted from the position indicator in synchronization with the timing of the tablet C, it can be recognized in an extremely shorter time than in the past, and it is faster than the first embodiment. An even larger number of switches, here 255 (excluding all "0" binary codes), can be provided.

FIG. 10 shows a third embodiment of the present invention, in which the P-8 conversion circuit of the position indicator in the second embodiment is replaced with a multiplexer.

That is, in the figure, 44 is a counter, 45 is a multiplexer, and these are connected to a coil 31, a capacitor 32, and a detector 3.
3. Waveform shaper 34, reset circuit 35, analog switch 38, flip-flop 40, code generator 41 and capacitor 43 constitute position indicator E. Note that the table soto is the same as that of the second embodiment.

The counter 44 divides the output pulse of the waveform shaper 34 by 1/
8. The frequency is divided into 1/16 and 1/32 and output, and is reset by the output of the reset circuit 35. The multiplexer 45 has 1/8, 1/16 and 1/3 of the counter 44.
The code generator 4 uses the divided-by-2 output as a 3-bit switching signal.
The binary code starting from 1 is switched and sent to the analog switch 38.

FIG. 11 shows the signal waveforms of each part in this embodiment, except for the switching signals v, w, and x of the counter 44, which are the same as in the second embodiment, and their functions and effects are also the same as in the second embodiment. Similar to the example.

In addition, since the value corresponding to the reference phase can also be obtained in the second and third embodiments, the phase can be changed in accordance with the operation as in the first embodiment, and this can be combined with the detection. You can also do that.

Further, the number of bits of the binary code in the second and third embodiments is merely an example, and it goes without saying that the number of bits is not limited to this.

(Effects of the Invention) As explained above, according to the present invention, the tablet transmits a radio wave capable of generating an induced voltage including predetermined timing information in the tuned circuit of the position indicator, and the position indicator uses the predetermined timing information. The information is extracted, the phase angle or frequency of the tuned circuit is changed based on the operation of a switch, etc. at a specific timing based on this information, and the phase angle of the radio wave from the tuned circuit is changed on the tablet side in synchronization with the specific timing. Or frequency is detected, so at least two pieces of information indicating the operating status of switches, etc. can be transmitted from the position indicator to the tablet without error, thereby eliminating errors caused by changes in the surrounding environment, etc. This makes it possible to transmit more operation information such as Swiss and Sochi.

Furthermore, if the phase angle or frequency of the tuned circuit is changed according to a specific code corresponding to the operation of a switch, etc., it is possible to transmit even more operation information of a switch, etc. in a short time. For example, there are advantages such as being able to configure a cordless keyboard device that can operate on a tablet.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a first embodiment of a position detection device and its position indicator according to the present invention, Fig. 2 is a block diagram showing an example of a conventional position indicator, and Fig. 3 is a block diagram showing a conventional position indicator. FIG. 4 is a flowchart of processing in the processing device of the first embodiment, FIG. 5 is a signal waveform diagram of each part in the first embodiment, and FIG. A configuration diagram showing the second embodiment, FIG. 7 is a circuit diagram showing a specific example of the code generator, and FIG.
The figure is a flowchart of processing in the processing device of the second embodiment, FIG. 9 is a signal waveform diagram of each part in the second embodiment, and FIG.
The figure is a configuration diagram showing a third embodiment of the present invention, and FIG. 11 is a signal waveform diagram of each part in the third embodiment. 21...Sense unit, 22...Selection circuit, 23...
Transmission/reception switching circuit, 24... Oscillator, 25... Voltage detection circuit, 26... Phase comparator, 27.28... Processing device, 31... Coil, 32.43. C1 to Cn-capacitor, 33... Envelope detector, 34... Waveform shaper, 35... Reset circuit, 36, 39.44...
・Counter, 37...AND gate, 38...analog switch, 40...flip-flop, 41...
- Code generator, 42...Parallel-serial conversion circuit, 45...Multiplexer, 81~Sn...Switch.

Claims (6)

[Claims] (1) In a position detection device consisting of a position indicator having at least a tuning circuit and a tablet that obtains coordinate values of a specified position by alternately transmitting and receiving radio waves to and from the position indicator, the tuning circuit of the position indicator means for transmitting a radio wave capable of generating an induced voltage containing predetermined timing information; and means for detecting the phase angle or frequency of the radio wave generated by the tuned circuit of the position indicator at a specific timing based on the predetermined timing information. and a means for extracting predetermined timing information from the induced voltage generated in the tuned circuit, and a means for extracting predetermined timing information from the induced voltage generated in the tuned circuit, and a means for extracting the phase angle or frequency of the tuned circuit based on the operation of a switch or the like at a specific timing based on the predetermined timing information. A position detecting device characterized in that a position indicator is provided with means for changing the position. (2) A tablet equipped with means for intermittently transmitting radio waves for a certain period of time that can cause the peak value of the tuning circuit of the position indicator to continuously generate an induced voltage of a certain level or higher for a longer period of time than during position detection; A position indicator is provided with a means for extracting as predetermined timing information an induced voltage whose peak value generated in the circuit is at a certain level or higher and which is continuous for a longer time than during position detection. 1) The position detection device described above. (3) A tablet equipped with a means for converting changes in phase angle or frequency detected at a specific timing into a code, and a means for changing the phase angle or frequency of a tuned circuit according to a specific code according to the operation of a switch, etc. Claim (1) or (2) characterized in that it is provided with a position indicator provided therein.
The position detection device described. (4) a tuned circuit; a means for extracting predetermined timing information from the induced voltage generated in the tuned circuit; and a means for extracting predetermined timing information from the induced voltage generated in the tuned circuit; and a means for changing the frequency. (5) The device according to claim (4), further comprising means for extracting, as predetermined timing information, an induced voltage whose peak value occurring in the tuned circuit is above a certain level and which is continuous for a longer time than during position detection. position indicator. (6) The position indicator according to claim 4 or 5, further comprising means for changing the phase angle or frequency of the tuning circuit according to a specific code corresponding to the operation of a switch or the like.