JPS6137817B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a specific signal transmitting/receiving device having a function of transmitting a specific information signal via broadcast radio waves, detecting the specific information signal on the receiving side, and automatically controlling audio output accordingly. .

An example of this type of transceiver is an emergency broadcast transceiver. This is a system in which when a specific code is sent out from a broadcasting station in the event of an emergency such as an earthquake or tsunami, the receiver detects this and listens to this information with priority. Even if the receiver switch is disconnected (however, the high frequency section and detection section are always operating, and only the low frequency section is disconnected), it will automatically enter the operating state.
This allows you to listen to the emergency information mentioned above.

However, if a signal similar to the above specific code is input to this type of receiver due to a prank or jamming in addition to the regular broadcast waves, the receiver will respond and the sound other than the emergency broadcast will be transmitted to the speaker. This may cause confusion on the part of the listener. In particular, if the above-mentioned specific code exists in the same frequency band as a general broadcast program, it can be easily recorded with a commercially available tape recorder when the above-mentioned specific code is broadcast, and prank radio waves can be generated based on this tape. It is quite possible that it will be fired.

The present invention relates to a method for preventing this type of receiver from malfunctioning due to the above-mentioned tampering or jamming waves. Below, regarding the present invention,
This will be explained with reference to drawings of examples. FIG. 1 shows a block diagram of a signal transmitting and receiving apparatus according to the present invention.

In the transmitter shown in the figure, the outputs of the emergency broadcast start code generator 1, information signal transmitter 3, and end code generator 4 are mixed in a mixer 5, and a modulator 6 modulates the carrier wave obtained from the carrier wave generator 8. . The output of the modulator 6 passes through a carrier wave interrupter 7 controlled by a carrier wave interrupter 2 and a transmitter 9, and is emitted as a radio wave from a transmitting antenna 10. Transmission section 9
An example of the output signal is shown in Fig. 2, where the start code, carrier wave intermittent, start code, emergency news announcement, and end code are arranged in the order, forming a series of emergency broadcast signals. . On the other hand, in the receiving section of FIG. 1, emergency broadcast radio waves are caught by the receiving antenna 15, and
6 is amplified and detected. Among these, the start code and the end code are discriminated by a code discriminator 19,
Its output goes "high level" with the start code and returns to "low level" with the end code. Furthermore, carrier wave discontinuity is determined by a carrier wave discontinuity discriminator 20. The carrier wave discontinuity discriminator 20 detects, for example, a change in the AGC voltage of an RF amplifier or an IF amplifier, counts the number of times this change occurs, and if a predetermined number of times is detected, the output is set to a "high level" and the above-mentioned ends. This can be realized with a circuit configuration that is reset to "low level" by the code discrimination output. The output of the carrier discontinuity discriminator 20 and the output of the code discriminator 19 obtained in this way are supplied to an AND gate 21, which drives the control switch 22 only when both outputs are at "high level". The low frequency amplifying section 17 becomes operational when the control switch 22 is turned on, and the emergency information detected by the receiving section 16 is transmitted to the listener as audio from the speaker 18.

In this way, in the present invention, the start of emergency broadcasting is communicated using intermittent carrier waves, but this is a signal component that does not appear at the output or detection output end of a normal radio or tuner, and as explained at the beginning. This greatly reduces the possibility that a specific code for such an emergency broadcast will be recorded on a commercially available tape recorder and used as a prank radio wave. Moreover,
According to the present invention, since a start code, an end code, and intermittent carrier waves are used together, troubles such as malfunction (operating when it shouldn't be) and non-operation (not operating when it should be) are extremely rare. You can obtain the excellent effect of becoming more resistant to interference. Although FIG. 2 shows the arrangement of signals to be transmitted, it is also possible to repeat the combination of the start code and carrier intermittent multiple times before the information announcement starts, if necessary.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the transmitting/receiving device of the present invention, and Fig. 2 shows one example of the contents of the signal to be transmitted.
It is an explanatory diagram showing an example. 1... Start code generator, 2... Carrier wave intermittent controller, 4... End code generator, 19... Code discriminator, 20... Carrier wave intermittent discriminator.

Claims (1)

[Claims] 1. By sending a predetermined information code from the transmitting side and detecting the predetermined information code on the receiving side,
In a specific signal transmitting/receiving device configured to control the output level of a low frequency amplification section, the transmitting side includes a start and end code generator, a carrier wave intermittent controller,
It is equipped with an information signal transmission section, starts broadcasting by a combination of start code modulation and carrier wave discontinuity, and ends broadcasting by end code modulation, and is equipped with a start and end code discriminator and a carrier wave discontinuity discriminator on the receiving side. 1. A specific signal transmitting/receiving device, comprising: an output level of a low frequency amplification section based on the outputs of both of the discriminators.