JPS6229352A - Call talking system - Google Patents

Abstract

PURPOSE:To prevent noise of a talking device to be called by providing a timer clearing storage content of a storage circuit when no code is generated for a prescribed time or over and a comparator circuit comparing the content of the storage circuit with a preset code and outputting a coincidence signal when they are coincident. CONSTITUTION:A timer 7 counts always and is reset only when a signal is outputted from a DTMF detection circuit 5 and counts up again when the signal is lost and clears the storage circuit 6 after a prescribed time. When a DTMF switch pad 1 of a call talking device generates continuously a code, the talking device to be called recognizes it as a consecutive code and when the code is sent for a prescribed time on the way, the talking device to be called regards it as the end of code transmission and prepares for the next reception. A comparison circuit 8 compares the code stored in the storage circuit 6 with the code specific to each device preset by a switch 9 and when they are coincident, a drive signal of an external ringing element 10 is outputted. Thus, noise problem in an independent talking device to be called is prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a system in which two or more handsets are connected on a party line through a wired or wireless line, and calls can be made directly to any handset without going through an exchange. The present invention relates to a calling system for making calls.

[Conventional technology]

Conventionally, for this type of call, a single frequency is transmitted by pressing a button switch attached to each handset, and the called handset transmits a unique frequency signal prepared for each handset. A method in which a ringing tone is sent to the speaker only when a single frequency from a calling station is detected for a certain period of time or longer in order to distinguish it from a voice frequency in a single frequency detection circuit, or a direct calling method by voice using a speaker. was used.

[Problem that the invention seeks to solve]

With the single-frequency paging system described above, the limited bandwidth voice circuit requires only 10 to 20 intercoms.
In addition, in the case of voice, the ringing tone is emitted to stations other than the called station, causing problems in terms of noise.

[Means for solving problems]

The calling system of the present invention includes a DTMF switch pad and a DT which receives a code obtained when the switch of the DTMF switch pad is pressed and generates DTMF.
An MF oscillation circuit is provided on the call device side, and the oscillation output of the DTMF oscillation circuit is received through the line, and a low-pass filter cuts unnecessary noise components and passes only the necessary frequency components. Obtained DTM
A DTMF detection circuit that detects F and generates a code, a memory circuit that stores the contents every time this code is generated, and a memory circuit that stores the tα circuit when no code is generated for a preset period of time. A timer to clear the contents,
Compare the contents of the memory circuit with the preset code,
It has a comparison circuit that outputs a match signal when there is a match, and a ringing element that is activated when the match signal is output.

As described above, since the method according to the present invention basically uses a code method, it is theoretically possible to connect an infinite number of intercoms, and since only the called intercom can generate a ringing tone, it is possible to connect an infinite number of intercoms. The noise problem in the called device is eliminated.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the main parts of an embodiment of the calling system of the present invention.

The 12-key DTMF switch pad 1 used in a smartphone is usually sufficient. The DTMF oscillation circuit 2 generates DTMF in response to the code obtained when the switch on the DTMF switch pad 1 is pressed. D
The TMF detection circuit 5 reproduces the code generated when the DTMF switch pad is pressed from the DTMF, stores this in the storage circuit 6, and at the same time outputs a signal to the timer 7 indicating that the code has been generated. The timer 7 is constantly counting, and is reset only when a signal is output from the DTMF detection circuit 5, but when the signal is no longer present, the timer 7 counts up again, and after a certain period of time, sends a clear signal to the memory circuit 6. and clears the memory circuit 6.

Here, it is considered that the appropriate period of time is about several seconds. Therefore, the DTMF switch pad 1 of the call intercom
If the code is being generated continuously, the called handset recognizes it as a continuous code, but if the code transmission stops for a certain period of time in the middle, the called handset assumes that the code transmission has ended. We will prepare for the next reception. Comparison circuit 8 compares the code stored in memory circuit 6 with the code unique to each handset set in advance by switch 9, and if they match, sends a signal to drive an external ringing element 10 (buzzer or bell). Output.

〔Effect of the invention〕

As explained above, the present invention uses a code system.

By making such a call, it is theoretically possible to connect an infinite number of handsets, and since only the called handset can generate a ring tone, the noise problem caused by unrelated called handsets is eliminated. It has the effect of

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the essential parts of the calling system of the present invention. 1...DTMF switch pad, 2...DTMF oscillation circuit, 3...Line, 4...
・Low pass filter, 5... DTMF detection circuit, 6... Memory circuit, 7
...Timer, 8...Comparison circuit, 9...
Switch, 10... ringing element.

Claims (1)

[Claims] DTMF switch pad and the code obtained when the switch of this DTMF switch pad is pressed, D
A DTMF oscillation circuit that generates TMF is provided on the call device side, and a low-pass filter that receives the oscillation output of the DTMF oscillation circuit through the line, cuts unnecessary noise components, and passes only the necessary frequency components; A DTMF detection circuit that detects the DTMF obtained through the low-pass filter and generates a code, a memory circuit that stores the contents every time this code is generated, and a code that is not generated for a preset period of time or more. a timer that clears the memory contents of the memory circuit in case of a match; a comparison circuit that compares the contents of the memory circuit with a preset code and outputs a match signal if they match; and a comparison circuit that operates when the match signal is output. 1. A calling system, characterized in that a ringing element is provided on a called device side.