JPH0346580Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial field of application> The present invention relates to an audio mixing circuit that superimposes a second audio signal from an audio synthesizer or the like onto an audio signal received by a television receiver, radio receiver, etc. It is.

<Summary of the invention> The present invention utilizes division of circuit impedance to superimpose a second audio signal from a speech synthesizer or the like onto a received audio signal. The purpose of the present invention is to provide a circuit that can effectively attenuate only the received audio.

<Conventional technology> In recent years, advances in semiconductor technology have led to the development of speech synthesizers.
It has been made into an IC, has become cheaper, and has been introduced into the consumer equipment field. Recently, some receivers such as television receivers have been commercialized and equipped with a speech synthesizer.

Conventionally, in this type of receiver, when outputting a second audio signal from a speech synthesizer, it is superimposed on the receiver's own audio signal, but in this case, it has been difficult to identify the content. Therefore, the period switching circuit for outputting the second audio signal from the audio synthesizer is used to completely erase the audio signal of the receiver itself, thereby improving identification.

<Problems to be solved by the invention> However, such conventional audio mixing circuits had complicated circuit configurations and decreased reliability.

<Means for Solving the Problems> The present invention was devised in view of the above points, and is an audio system that can mix two audio signals using a relatively simple circuit and improve voice discrimination. It provides a mixed circuit.

<Example> The present invention will be described below according to an example shown in the drawings. FIG. 1 shows a circuit diagram of an embodiment of the present invention,
Further, FIG. 2 shows a signal waveform diagram in the same embodiment.

In FIG. 1, 1 is the input terminal for the first audio signal received by the receiver itself, 2 is the input terminal for the second audio signal generated by a speech synthesizer, etc., and 3 is the input terminal for the second audio signal received together with the resistor 4. A transistor 5 constitutes an emitter follower amplifier for audio amplification, and a transistor 5 constitutes an emitter follower amplifier for second audio amplification together with a resistor 6. Also, 7 is input terminal 2
an input terminal 8 for applying a switching pulse _e3 that is "H" during the period when the second audio signal is supplied to the input terminal 8;
1 is a switching transistor forming a switching circuit together with a resistor 9; 10 is an audio amplifier for amplifying a mixed audio signal; and 11 is an audio output terminal.

In steady state, the first signal received by the receiver
The audio signal _e1 is supplied to the input terminal 1, is amplified by the transistor 3, and then connected to the resistor 12 from the emitter.
The signal is taken out via a capacitor 13 and further supplied to the audio amplifier 10 via a capacitor 14. During this steady state, the input terminal 7 is at the "L" level, so the switching transistor 8 is in an off state, and the impedance _Z3 seen from the connection point to the collector side of the transistor 8 is extremely high.
Therefore, in this case, a signal having approximately the same level as the audio signal applied to input terminal 1 is obtained at the connection point.
The input/output waveforms of each part in this case are shown by the periods in FIG.

Now, when a second audio signal generated by a voice synthesizer or the like is applied to the input terminal 2 and an "H" pulse is applied to the input terminal 7, the transistor 8 is turned on during this time, and the impedance Z ₃ decreases. Here, if the impedance seen from the connection point to the emitter side of transistor 3, that is, the output impedance of the receiving audio circuit, is Z ₁ , and the input signal of the receiving audio is e ₁ , then the signal level e ₄₁ at the connection point is e ₄₁ = Z ₃ /Z ₁ +Z ₃ e ₁ …(1).

Next, if the impedance seen from the connection point to the emitter side of the transistor 5, that is, the circuit impedance of the second audio signal from a voice synthesizer etc., is Z ₂ , and the input signal of the second audio is e ₂ , then the signal at the connection point is The level e ₄₂ is e ₄₂ =Z ₃ /Z ₂ +Z ₃ e ₂ (2).

Here, if the values of each resistor 4, 6, 9, 12, etc. are set in advance so that the relationship between each impedance is Z ₂ ≪ Z ₁ , Z ₃ ...(3), the above equation (2) becomes e ₄₂ e ₂ …(4).

In other words, the received first audio signal e ₁ is attenuated by the division ratio of the two impedances Z ₁ and Z ₃ as shown in equation (1) above, while the second audio signal generated by a speech synthesizer etc. e ₂ is mixed at the connection point with almost no attenuation, and the mixed signal e ₄ thus mixed is supplied to the audio amplifier 10.
The waveforms of each part in this case are shown by periods in FIG.

<Effects of the invention> As described above, according to the audio mixing circuit of the invention,
With a relatively simple circuit configuration using three transistors, it is possible to attenuate and mix only the received audio signal without attenuating the second audio signal from a speech synthesizer etc. by utilizing circuit impedance division. This improves its identification.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a signal waveform diagram of each part of the embodiment. 1...First input terminal, 2...Second input terminal, 3
...Transistor for receiving audio amplification, 5...Transistor for second audio amplification, 7...Third input terminal, 8
...Switching transistor.

Claims (1)

[Claims for Utility Model Registration] A first audio signal e ₁ received by a receiver including a transistor 3 configured as an emitter follower amplifier.
a second audio amplifier 5, 6 that includes a transistor 5 configured as an emitter follower amplifier and amplifies a second audio signal _e2 generated by an audio synthesizer or the like; and a transistor 8. The transistor 8 is controlled to be turned on and off based on a switching pulse _e3 responsive to the presence or absence of the second audio signal _e2 .
a switching circuit 8, the collector of which is connected to a connection point that mixes the output signals of the receiving audio amplifiers 3, 4 and the output signals of the second audio amplifiers 5, 6;
9, an impedance Z ₁ seen from the connection point to the transistors 3 of the receiving audio amplifiers 3 and 4, an impedance Z ₂ seen from the connection point to the transistors 5 of the second audio amplifiers 5 and 6, and the connection The relationship between the impedance Z ₃ and the transistor 8 of the switching circuits 8 and 9 from the point is set so that Z ₂ << Z ₁ , Z ³ so that the second audio signal e ₂ is not attenuated. An audio mixing circuit characterized in that the second audio signal e ₂ and the first audio signal e ₁ are mixed with the first audio signal e ₁ in a state where the first audio signal e 1 is attenuated.