CA1094164A - Radio signalling systems - Google Patents
Radio signalling systemsInfo
- Publication number
- CA1094164A CA1094164A CA274,074A CA274074A CA1094164A CA 1094164 A CA1094164 A CA 1094164A CA 274074 A CA274074 A CA 274074A CA 1094164 A CA1094164 A CA 1094164A
- Authority
- CA
- Canada
- Prior art keywords
- carrier frequency
- burst
- cycles
- tokens
- count
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Mobile Radio Communication Systems (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A radio signaling system includes a number of portable tokens each capable of transmitting signals in the form of a carrier frequency which is common to the tokens, with spaced modulation pulses superimposed on the carrier and dunning a carrier burst between successive of said pulses.
The number of carrier frequency cycles in a carrier burst between successive modulation pulses is different for different tokens, although for any one token the number of carrier frequency cycles is the same in each burst of transmitted signals. A receiver its provided which is capable of distinguish-ing between received signals from tokens with different characteristic numbers of cycles in their bursts. Such a system is particularly suited for use in an identity system or an alarm system.
A radio signaling system includes a number of portable tokens each capable of transmitting signals in the form of a carrier frequency which is common to the tokens, with spaced modulation pulses superimposed on the carrier and dunning a carrier burst between successive of said pulses.
The number of carrier frequency cycles in a carrier burst between successive modulation pulses is different for different tokens, although for any one token the number of carrier frequency cycles is the same in each burst of transmitted signals. A receiver its provided which is capable of distinguish-ing between received signals from tokens with different characteristic numbers of cycles in their bursts. Such a system is particularly suited for use in an identity system or an alarm system.
Description
This invention relates to radio signalling systems where it is necessary to be able to distinguish between different individuals.
One application of such a system is where any one of a number of individuals for example, old people may wish to summon assistance and it is necessary for someone at the re-ceiver to be able to identify which person caused the alarm.
Another application is where only certain people are to have access to a security area and it is necessary for a receiver to be able to distinguish between those people and other people.
In each case each person using the system can have a portable pocket token for generating radio signals when assistance is required or when access to the security area is required as the case may be.
An object of the invention is to provide a partic-ularly simple and economical way of distinguishing between different pocket tokens even when there are a large number of tokens on the system.
According to the present invention a radio signalling system includes a number of portable tokens each capable of transmitting signals in the form of a carrier frequency which is common to the tokens, with spaced modulation pulses super-imposed on the carrier and defining a carrier burst between successive of said pulses, the number of carrier frequency cycles in a carrier burst between successive modulation pulses being different for different tokens, and a receiver capable of distinguishing between received signals from tokens with different characteristic numbers of cycles in their burst, wherein for any one token the number of carrier frequency cycles is the same in each burst of transmitted signals.
~1 ~..
Thus distinction between different individuals or different tokens is provided merely by different numbers of carrier frequency cycles ~etween successive modula-tion -2a-.~ ~
~ ` , .
pulses which merely serve to limit the period over which the cycles are to be counted, and can also operate logic circuits both in the transmitters and in the receiver.
The system is thus very simple and yet enables 5. very large numbers of people to use the syste~ because the separation between channels, that is to say between the numbers of carrier frequency cycles in bursts of similar tokens can be quite small. In spite of that the equipment is guite economical in manufacture.
10. For example a permissible range of ~requencies is 50 K~z - 150 KHz and as a 5KHz separation between carrier frequencies is satisfactory, there are 20 frequencies available. A 6-bit binary counter has a count of 64, and a preliminary multi-bit binary counter may be used as a 15. divided of carrier cycles for driving the 6-bit counter.
That would give 20 x 6~ or 1280 'differs' on the system.
A suitable transmitter output power is 5 milli watts, which would not cause substantial drain on the token batteries, nor unacceptable interference outside the area 20. where the system is being used.
The invention may be carried into practice in various ways and three embodiments will now be described by way of example with reference to the accompanying drawings in which;
25- FIGURES 1 and 2 are respective logic circuits for an access system and an alarm system; and FIGURE 3 is a circuit for an alternatlve access system.
In both embodiments each user of the system has 30- a portable token containing a simple radio transmitter working on a common radio frequency channel, and arranged to modulate a-radio frequency by a 1 millisecond pulse at regular intervals of a certain number of radio frequency cycles, the particular number being unique to that user 5. or to the users in a particular group of users. In the example being described the modulation is amplitude modulation, but it could equally well be phase or frequency modulation.
The user may switch his transmitter on manually 10. when he wants to obtain access to a secure area or when he wants to give an alarm as the case may be, and t~le modulated radio frequency is transmitted from a'suitable integral aerial. Alternatively the transmitter could be left on continuously.
15. Signals are received by an inductive loop signalling band or by some other convenient means and supplied,to a réceiver which in the case of the access system is a~r~nged in accordance with F~GURE 1 to determine if the number of radio frequency cycles received between successive 20. : modulation pu]ses agrees wlth a pre-set number in which case an operating circuit releases the entrance to the prohibited area.
The received signals are amplified with automatic gain control at 11 attenuated at 12 and fed into a phase-25. locked loop system 13 having fine and coarse tuning means.
The received radio frequency cycles or a knownsub-multiple or difference frequency from them are amplified at 15 and used as clock pulses for driving a series of binary coded decimal counters 16, 17 and 18., and control 30~ of ~he ~irst counter 16 is by means of a monostable circuit 19, a flip-flop 21 and a NAND gate 22. A received modulation pulse is amplifled at 15' triggers the monostable circuit 19 and that is arranged to provide an input to the NAND gate ready for re-setting the first countcr 5. 16 which receives clock pulses and provides control signals for the remainder of the system.
The first control signal is obtained from the 2 output of the counter 16 and enables a compara'cor 23 which compares the count achieved on the later coun~ers 17 and 10. 1~3 in the previous burst of carrier radiation between pulses with the pre-set count as set at 24. The first control signal is also fed to a decade counter 25 for counting the number of comparisons made. If the comparator 23 shows coincidence, the count of a counter 26 is 15. increased but if it does not show coincidence, the count ; is decreased and when the count of the counter 26 reaches 4 showing that 4 successful comparisons have been made, a flip~
flop 27 is operated which controls operation of a circuit ; 28 for giving access to the security area.
~0, ~ The second control signal from the number 6 output of the counter 16 renders the counter 17 receptive to .
clock pulses and an output from that counter 17 in turn renders the counter 18 receptive, so that the total count of clock pulses in the interval between two successive 25. modulation pulses is recorded on the two most significant stages C.D. of the counter 17 and the A.B.C.D. stages of the counter 18 for subsequrnt comparison with the pre-set value in the comparator 23. The comparison is made from the 2 output of the counter 16 before the 30. counters 17 and 18 are re-set from the 6 output of the .
-5~
` counter 16 and start to be refilled. The 7 output from the counter 16 is used to re-set the flip-flop 21 to provide an input to the NAND ga~e 22 to re-set the counter 16 when it has fulfilled its function.
A re~set button 29 disconnects the circuit 28 and resets the circuit ready for the next operation.
The logic circuit shown in FIGURE 2 for a recelver for the alarm system is very similar to the circuit described with reference to FIGURE 1 and corresponding components .o have been given the same numerals. In this case however instead of operating an entrance to a security area, it is desired to give a warning and a display of the identity of the individual whose token initiated the alarm. The token must only be operated when an alarm is required. The 15. alarm circuit corresponds with the operating circuit 2~3 in FIGURE l but the identity display is given on a 3 digit display unit 31 which receives a count for determining the display from the counter 17 by way of the comparator 23 at its Al input.
20. : ~ However, the display is only given when a blanking si~nal is removed in response to operation of the flip-flop 27 after the counter 26 has shown that 4 success~ul comparisons have been Inade. In this case the comparison is not with a pre-set number, but with the count in the preceding sample.
25. Thus after each sample of radio frequency, transmission the count achieved on ~he counters 17 and 18 is transferred to a store 33 in response to a signal from the number ~ output of the counter 16. The next count is compared at 23 with the stored count and if identity is shown, an output signal increases the count of the counter 26 in the same way as described with reference to ~GURE l.
~34~
A nu~nber of' refinements may be added to the b~sic circuit; counts of les.s or more than a present value on the subsequent counting stages can be deemed present due to interference and the sample ignored or a decrement applied 5. to the final counter. A tuning indicator can be provicled consisting of an exclusive or gate connected to the outputs of the two binary stages immediately prior to the least significant active stage. If modulating pulses are nicely centred in their channel an output will be present at this 10. gate and can be used to illuminate a 'tuned' indicator.
Each transmitter can be provided with two modulating co~lnts, preferably on adjacent c'hannels, so that a final response a-t the receiver of an odd count represents an alarm of higher urgency than an even count (or vice versa).
15. In the display the least significant active count bit is not displayed as count, but as ~degree of urgency'.
The re-set button in the access system of EIGURE 1 co~lld be a timing circuit to automatically reset the system after a pre~set time, irrespective of whether 20. access had been gained or not.
In th'e simplified version of FIGURE 1 shown in FIGURE 3 similar numerals have been used for similar components The radio-f`requency cycles ampli~ied at 42 are used a control logic arrangement 41 to provide clock pulses for 25. counting by the counter 43 which is a 12 bit binary counter, the last six units ~16 of which are used to provide a'count for comparison. Thus 64 cycles are received before the counter 46 increases its count by 1, and the counter 46 has a total count of 26 or 64.
30. . The f~irst few c~cles at 42 af'ter a modulatlon pulse at l5 are used as timing sequence control signals from the control logic 41 and do not affect the count of the counter 46.
The first control signal enables the comparator 5. 23 which compares the count achieved on the counter 46 in the previous burst of carrier radiation with the pre~set count as set at 24. 'i'he f`irsk control signal is also fed to counters 44 and 45. If comparator 23 shows coincidence the counk of counter 44 is increased. If the lO. comparator does not show coincidence the count at counter 45 is increased. When the count on counter 44 reaches four showing that four successful comparisons have been made the flip-flop 27 is operated which controls operation of the circuit 23 for controlling an external mechanism.
15. If the count on counter 45 passes a pre-set value indicating that several incorrect comparisons have been made counter 44 will be re-set to zero and also an AGC circuit at ~F amplifier ll wlll be actuated to desenslti%e the input.
The second control signal from the control logic B 20. ~ renders the counter 43 receptive to clock pulses so that the total count of clock pulses in the interval between two successive modulation pulses is recorded and l/64th of that count is recorded on the si~ most significant stages of counter 43 - the counter 46 -25. for subsequent comparision with the pre--set value at 24 in the comparator 23.The comparision is made on the first output of the contro3 logic before the counters are re-set and start to be refi:lled from the second output of the control logic.
30. The third output of the control logic is used to ~3-.. . .
re-set the control lo~ic to prepare for the reception of the next modulation pulse. A reset push-button 29 or a timing circuit disconrlects the circuit 28 and resets the circuitry ready for the next operation.
5.
One application of such a system is where any one of a number of individuals for example, old people may wish to summon assistance and it is necessary for someone at the re-ceiver to be able to identify which person caused the alarm.
Another application is where only certain people are to have access to a security area and it is necessary for a receiver to be able to distinguish between those people and other people.
In each case each person using the system can have a portable pocket token for generating radio signals when assistance is required or when access to the security area is required as the case may be.
An object of the invention is to provide a partic-ularly simple and economical way of distinguishing between different pocket tokens even when there are a large number of tokens on the system.
According to the present invention a radio signalling system includes a number of portable tokens each capable of transmitting signals in the form of a carrier frequency which is common to the tokens, with spaced modulation pulses super-imposed on the carrier and defining a carrier burst between successive of said pulses, the number of carrier frequency cycles in a carrier burst between successive modulation pulses being different for different tokens, and a receiver capable of distinguishing between received signals from tokens with different characteristic numbers of cycles in their burst, wherein for any one token the number of carrier frequency cycles is the same in each burst of transmitted signals.
~1 ~..
Thus distinction between different individuals or different tokens is provided merely by different numbers of carrier frequency cycles ~etween successive modula-tion -2a-.~ ~
~ ` , .
pulses which merely serve to limit the period over which the cycles are to be counted, and can also operate logic circuits both in the transmitters and in the receiver.
The system is thus very simple and yet enables 5. very large numbers of people to use the syste~ because the separation between channels, that is to say between the numbers of carrier frequency cycles in bursts of similar tokens can be quite small. In spite of that the equipment is guite economical in manufacture.
10. For example a permissible range of ~requencies is 50 K~z - 150 KHz and as a 5KHz separation between carrier frequencies is satisfactory, there are 20 frequencies available. A 6-bit binary counter has a count of 64, and a preliminary multi-bit binary counter may be used as a 15. divided of carrier cycles for driving the 6-bit counter.
That would give 20 x 6~ or 1280 'differs' on the system.
A suitable transmitter output power is 5 milli watts, which would not cause substantial drain on the token batteries, nor unacceptable interference outside the area 20. where the system is being used.
The invention may be carried into practice in various ways and three embodiments will now be described by way of example with reference to the accompanying drawings in which;
25- FIGURES 1 and 2 are respective logic circuits for an access system and an alarm system; and FIGURE 3 is a circuit for an alternatlve access system.
In both embodiments each user of the system has 30- a portable token containing a simple radio transmitter working on a common radio frequency channel, and arranged to modulate a-radio frequency by a 1 millisecond pulse at regular intervals of a certain number of radio frequency cycles, the particular number being unique to that user 5. or to the users in a particular group of users. In the example being described the modulation is amplitude modulation, but it could equally well be phase or frequency modulation.
The user may switch his transmitter on manually 10. when he wants to obtain access to a secure area or when he wants to give an alarm as the case may be, and t~le modulated radio frequency is transmitted from a'suitable integral aerial. Alternatively the transmitter could be left on continuously.
15. Signals are received by an inductive loop signalling band or by some other convenient means and supplied,to a réceiver which in the case of the access system is a~r~nged in accordance with F~GURE 1 to determine if the number of radio frequency cycles received between successive 20. : modulation pu]ses agrees wlth a pre-set number in which case an operating circuit releases the entrance to the prohibited area.
The received signals are amplified with automatic gain control at 11 attenuated at 12 and fed into a phase-25. locked loop system 13 having fine and coarse tuning means.
The received radio frequency cycles or a knownsub-multiple or difference frequency from them are amplified at 15 and used as clock pulses for driving a series of binary coded decimal counters 16, 17 and 18., and control 30~ of ~he ~irst counter 16 is by means of a monostable circuit 19, a flip-flop 21 and a NAND gate 22. A received modulation pulse is amplifled at 15' triggers the monostable circuit 19 and that is arranged to provide an input to the NAND gate ready for re-setting the first countcr 5. 16 which receives clock pulses and provides control signals for the remainder of the system.
The first control signal is obtained from the 2 output of the counter 16 and enables a compara'cor 23 which compares the count achieved on the later coun~ers 17 and 10. 1~3 in the previous burst of carrier radiation between pulses with the pre-set count as set at 24. The first control signal is also fed to a decade counter 25 for counting the number of comparisons made. If the comparator 23 shows coincidence, the count of a counter 26 is 15. increased but if it does not show coincidence, the count ; is decreased and when the count of the counter 26 reaches 4 showing that 4 successful comparisons have been made, a flip~
flop 27 is operated which controls operation of a circuit ; 28 for giving access to the security area.
~0, ~ The second control signal from the number 6 output of the counter 16 renders the counter 17 receptive to .
clock pulses and an output from that counter 17 in turn renders the counter 18 receptive, so that the total count of clock pulses in the interval between two successive 25. modulation pulses is recorded on the two most significant stages C.D. of the counter 17 and the A.B.C.D. stages of the counter 18 for subsequrnt comparison with the pre-set value in the comparator 23. The comparison is made from the 2 output of the counter 16 before the 30. counters 17 and 18 are re-set from the 6 output of the .
-5~
` counter 16 and start to be refilled. The 7 output from the counter 16 is used to re-set the flip-flop 21 to provide an input to the NAND ga~e 22 to re-set the counter 16 when it has fulfilled its function.
A re~set button 29 disconnects the circuit 28 and resets the circuit ready for the next operation.
The logic circuit shown in FIGURE 2 for a recelver for the alarm system is very similar to the circuit described with reference to FIGURE 1 and corresponding components .o have been given the same numerals. In this case however instead of operating an entrance to a security area, it is desired to give a warning and a display of the identity of the individual whose token initiated the alarm. The token must only be operated when an alarm is required. The 15. alarm circuit corresponds with the operating circuit 2~3 in FIGURE l but the identity display is given on a 3 digit display unit 31 which receives a count for determining the display from the counter 17 by way of the comparator 23 at its Al input.
20. : ~ However, the display is only given when a blanking si~nal is removed in response to operation of the flip-flop 27 after the counter 26 has shown that 4 success~ul comparisons have been Inade. In this case the comparison is not with a pre-set number, but with the count in the preceding sample.
25. Thus after each sample of radio frequency, transmission the count achieved on ~he counters 17 and 18 is transferred to a store 33 in response to a signal from the number ~ output of the counter 16. The next count is compared at 23 with the stored count and if identity is shown, an output signal increases the count of the counter 26 in the same way as described with reference to ~GURE l.
~34~
A nu~nber of' refinements may be added to the b~sic circuit; counts of les.s or more than a present value on the subsequent counting stages can be deemed present due to interference and the sample ignored or a decrement applied 5. to the final counter. A tuning indicator can be provicled consisting of an exclusive or gate connected to the outputs of the two binary stages immediately prior to the least significant active stage. If modulating pulses are nicely centred in their channel an output will be present at this 10. gate and can be used to illuminate a 'tuned' indicator.
Each transmitter can be provided with two modulating co~lnts, preferably on adjacent c'hannels, so that a final response a-t the receiver of an odd count represents an alarm of higher urgency than an even count (or vice versa).
15. In the display the least significant active count bit is not displayed as count, but as ~degree of urgency'.
The re-set button in the access system of EIGURE 1 co~lld be a timing circuit to automatically reset the system after a pre~set time, irrespective of whether 20. access had been gained or not.
In th'e simplified version of FIGURE 1 shown in FIGURE 3 similar numerals have been used for similar components The radio-f`requency cycles ampli~ied at 42 are used a control logic arrangement 41 to provide clock pulses for 25. counting by the counter 43 which is a 12 bit binary counter, the last six units ~16 of which are used to provide a'count for comparison. Thus 64 cycles are received before the counter 46 increases its count by 1, and the counter 46 has a total count of 26 or 64.
30. . The f~irst few c~cles at 42 af'ter a modulatlon pulse at l5 are used as timing sequence control signals from the control logic 41 and do not affect the count of the counter 46.
The first control signal enables the comparator 5. 23 which compares the count achieved on the counter 46 in the previous burst of carrier radiation with the pre~set count as set at 24. 'i'he f`irsk control signal is also fed to counters 44 and 45. If comparator 23 shows coincidence the counk of counter 44 is increased. If the lO. comparator does not show coincidence the count at counter 45 is increased. When the count on counter 44 reaches four showing that four successful comparisons have been made the flip-flop 27 is operated which controls operation of the circuit 23 for controlling an external mechanism.
15. If the count on counter 45 passes a pre-set value indicating that several incorrect comparisons have been made counter 44 will be re-set to zero and also an AGC circuit at ~F amplifier ll wlll be actuated to desenslti%e the input.
The second control signal from the control logic B 20. ~ renders the counter 43 receptive to clock pulses so that the total count of clock pulses in the interval between two successive modulation pulses is recorded and l/64th of that count is recorded on the si~ most significant stages of counter 43 - the counter 46 -25. for subsequent comparision with the pre--set value at 24 in the comparator 23.The comparision is made on the first output of the contro3 logic before the counters are re-set and start to be refi:lled from the second output of the control logic.
30. The third output of the control logic is used to ~3-.. . .
re-set the control lo~ic to prepare for the reception of the next modulation pulse. A reset push-button 29 or a timing circuit disconrlects the circuit 28 and resets the circuitry ready for the next operation.
5.
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A radio signalling system including a number of portable tokens each capable of transmitting signals in the form of a carrier frequency which is common to the tokens, with spaced modulation pulses superimposed on the carrier and defining a carrier burst between successive of said pulses, the number of carrier frequency cycles in a carrier burst between successive modulation pulses being different for different tokens, and a receiver capable of distinguishing between received signals from tokens with different characteristic numbers of cycles in their bursts, wherein for any one token the number of carrier frequency cycles is the same in each burst of transmitted signals.
2. A system as claimed in Claim 1 in which for each token the number of carrier frequency cycles is the same in each burst of transmitted signals.
3. A system as claimed in Claim 1 in which the trans-mitter is small enough to go in a user's pocket.
4. A system as claimed in Claim 3 including a manual switch for causing the token to start transmitting.
5. A system as claimed in Claim 1 in which the carrier frequency is a radio frequency.
6. A system as claimed in Claim 5 in which the receiver includes a counter of clock pulses derived from the cycles in the burst of received carrier frequency.
7. A system as claimed in Claim 6 in which the receiver includes a comparator of the count achieved by the counter.
8. A system as claimed in Claim 7 in which the counter compares the achieved count with a pre-set count identifying tokens to which access is to be given to a security area.
9. A system as claimed in Claim 8 in which the receiver is arranged in response to a successful comparison to operate release mechanism to a security area.
10. A system as claimed in Claim 7 in which the comparator compares the achieved count with the count achieved in the preceding burst, of carrier frequency received.
11 A system as claimed in Claim 1 in which the receiver includes a display of a symbol identifying the number of cycles in a received burst of carrier frequency.
12. A system as claimed in Claim 2 in which the comparator operates on successive received bursts of carrier frequency and only operates thr alarm or operating circuit when a certain number of correct comparisons have been ade.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA274,074A CA1094164A (en) | 1977-03-16 | 1977-03-16 | Radio signalling systems |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA274,074A CA1094164A (en) | 1977-03-16 | 1977-03-16 | Radio signalling systems |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1094164A true CA1094164A (en) | 1981-01-20 |
Family
ID=4108170
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA274,074A Expired CA1094164A (en) | 1977-03-16 | 1977-03-16 | Radio signalling systems |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1094164A (en) |
-
1977
- 1977-03-16 CA CA274,074A patent/CA1094164A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |