JPS593799B2 - special calling device - Google Patents

Description

[Detailed Description of the Invention] This device is a wireless transmitter of weak radio waves that does not require a license.
This is a special paging device that automatically responds when a receiver that is continuously receiving transmitted signals without the "disconnection time" described later becomes separated from the transmitter by a certain distance and exceeds its reception capability limit. As an example, a transmitter can be built into an important personal item, and a receiver can be placed in one's breast pocket, etc. (This can be used to automatically issue a call alarm if the item is left behind or taken away.

However, it must be taken into consideration that external radio waves may cause interference to the receiver, and countermeasures against this are essential, but in conventional devices of this type, such countermeasures have not been taken or have been inadequate.

External radio waves include broadcast radio waves, various wireless communications, etc.
In general, it is a carrier frequency with low-frequency modulation by voice or musical tone, etc., and there are also cases where the carrier frequency is directly interrupted by a Morse code, etc., but these voices, musical tones, or Morse code etc. (hereinafter referred to as audio etc.) has a large number of "cutting times" for the following reasons.

In other words, while each voice has a unique frequency component, there is also a frequency band in which each voice is missing.For example, voices such as A, I, Tsu, Work, and O have their own unique missing frequency components between 300 and 2500H2. It is known that there is a range.

Therefore, if a specific band filter is used, the output of the audio signal that passes through this band will often be almost completely absent due to temporal changes in audio, etc., and this results in a "cutoff time." This is some of the scenes.

Syllables formed by sounds, etc. (5ylable)
Naturally, there are pauses in time at breaks between phrases and phrases, and no signal output is allowed during these pauses.

In any case, it has been found that in normal audio, etc., there is a time when these signals are not output, and if this is defined as "one disconnection time", the length of that time is almost 10 milliseconds or more.

(Reference Figures 11 to 14) For normal audio, etc., there is a "disconnection time" during one second.
Since it seems that it is always recognized at least once, (Reference No. 1)
(Figures 6 to 19) In the case of the combination of transmitter and receiver of the present invention, it is sufficient to transmit a continuous signal with no disconnection time as the transmission signal. It is sufficient to use C-R transmission.

The receiver is equipped with a disconnection time discrimination circuit to prevent erroneous operation due to external radio waves.

For this purpose, for example, as will be described in detail later, the circuit shown in FIG. 3 can automatically detect and discriminate when a signal with a disconnection time greater than 10 milliseconds is received.

In this way, a device that automatically issues an alarm when the receiver of the combination is separated from the transmitter by more than a certain distance from the situation where it is receiving continuous signals and the reception limit is exceeded is a device that automatically issues an alarm due to interference from external radio waves. Even if there is interference, it is possible to receive the above-mentioned continuation signal within the close distance of the transmitter/receiver, but if the distance exceeds a certain distance, the continuation signal cannot be received and only external radio waves can be received. The reception is also around 1 second, and as mentioned above, the disconnection time in the received signal can be detected and discriminated, so the conclusion is that it is possible to ``issue an alarm that there is no continuation signal''.

That is, even if there is interference from external radio waves, it can be used without causing any practical problems.

An example of implementation of the present invention will be described below with reference to the drawings.

Fig. 1 shows an outline of the arrangement of each part of the transmitter. 1 is a carrier frequency transmitting section, 2 is a transmitting section that generates a low frequency signal with no disconnection time by a C-R oscillation circuit, and 3 is a modulated amplification section. can be,
4 indicates the transmitting antenna.

Figure 2 shows an overview of the arrangement of each part of the receiver. 1 is a receiving antenna, 2 is a high frequency amplification section, 3 is a local oscillation section for superhetero reception, 4 is a mixed detection section, and 5 is an intermediate frequency amplification section. Part, 6
1 is a low frequency detection section, 1 is a low frequency amplification section, 8 is a low frequency specific band filter, and 9 is a disconnection time discrimination circuit section, so that a continuous signal (without disconnection time) from the transmitter is not received. Even if an external radio wave is received, the disconnection time in the low frequency signal passing through the filter 8 is detected and the alarm transmitter 10 is activated accordingly.

To be more specific, in Fig. 3, when the power supply 11 is turned on and the transmitting and receiving conditions are in use, if the continuation signal from the combined transmitter enters 12 as a signal after passing through the front stage circuit of the receiver, the transistor T1 ．． T2 responds and subsequently holds the thyristor T3 to prevent the alarm transmitter 10 from operating.

If the transmitter and receiver are separated and the continuation signal is not received (if not, T3 activates the alarm transmitter 10 and the alarm continues unless the reset 13 is pressed).

In this case, there is a concern that the external signal may interfere and cause interference, but if the values of C and R of the output circuit of T1 are set so that the time constant is, for example, about 1 to 2 ms, the external signal will always be present. At the same time as the included disconnection time of 1071 Ls or more appears, T2 acts as a trigger to activate the thyristor T3, and accordingly, the alarm transmitter 10 is also activated, so there is no fear of interference.

In the above cases, it is necessary to have a carrier frequency band and its specific modulation frequency band assigned to each combination of transmitter and receiver to prevent mutual interference with other combinations. be.

[Brief explanation of drawings]

Figure 1 shows the arrangement of each part of a transmitter as an example of implementing the present invention. Uses a C-R oscillation circuit. 3... Modulated amplification section that performs low frequency modulation on the carrier frequency and amplifies it; 4...
・Transmission antenna; Figure 2 shows the arrangement of each part of the receiver as an example of implementing the present invention; Figure 3 shows an example diagram of the disconnection time discrimination circuit section; 1...Reception antenna; 2... High frequency amplification section, 3... Local oscillation section, 4... Mixed detection section, 5... Intermediate frequency amplification section, 6...・・・
...Low frequency detection section, 7...Low frequency amplification section, 8.
...Low frequency specific band filter, 9...
・Disconnection time discrimination circuit section, 10... Alarm transmission section,
11... Cutting time discrimination circuit power supply, 12...
...Signal input section as above, 13...Reset.

Claims (1)

[Claims] 1 In the combination of the weak radio wave transmitter 8 and the receiver,
When the receiver receives interference from various external radio waves, by detecting and discriminating the various disconnection times inherent in the external signals, it can respond only to specific signals transmitted by the combination transmitter that do not have disconnection times. special call device.