JPS601985B2 - Transmitter microphone circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microphone circuit in a simplex communication system line transmitter.

As a transmitter microphone, dynamic
Microphones, carbon microphones, etc. are mainly used, but especially when using something that does not require a power supply, such as a dynamic microphone, the microphone circuit shown in the block diagram in Figure 1 is applied. . For convenience of explanation, the figure takes an FM transmitter as an example and shows its entire configuration. In the figure, the output of a dynamic microphone (hereinafter referred to as microphone) M is given to a low frequency amplifier AA, where it is amplified to a predetermined level and becomes a modulation signal of a modulator MOD, which converts it into a carrier wave from an original oscillator OSC. On the other hand, frequency modulation is performed, and the modulator MOD
The modulated wave from the output is multiplied to a predetermined frequency by the transmitter MUL, and then further amplified by the power amplifier PA and transmitted as a radio wave from the antenna ANT.

However, the press talk switch Sp connected to the transmitter control circuit CT is normally off, and therefore the transmission control circuit CT, which controls the power failure, does not operate, and as a result, the primary oscillator OSC, No power supply voltage is applied to the modulator MOD, the transmitter MUL, the low frequency amplifier AA, etc.
When the press talk switch Sp is turned on, the transmitter control circuit CT operates, and by this control, a power supply voltage is applied from within the power supply to each of the above-mentioned parts, so that the transmitter operates as a transmitter.

However, transmitters used in nearby wireless communication networks automatically call each other between wireless stations by transmitting individual paging signals, simultaneous paging signals, etc. using audio frequency signals, etc. For this purpose, a signal generator SG and a transmitter start switch Ss are added, and when the switch Ss is turned on, the transmitter control circuit CT operates, and the power supply PS
A power supply voltage is applied to each part of the transmitter from the transmitter, and the transmitter is brought into operation.

Therefore, even when the transmitter activation switch Ss is turned on and the signal from the signal generator SG is being transmitted, the microphone M is in an operating state and its output is being given to the low frequency amplifier AA. Nearby sound is signal generator SG
"The output from microphone M becomes noise and is superimposed and received by the other party, and the signal receiver of the other party malfunctions due to the noise from microphone M, and unnecessary audio is generated. There were disadvantages such as being transmitted.

The present invention has the purpose of fundamentally eliminating the above-mentioned drawbacks of the prior art, and in the microphone circuit of the transmitter as described above, the other end of the capacitor, one end of which is connected to the output side of the microphone, is normally connected by a press-to-talk switch. When connected to a common circuit, the microphone output is bypassed by a capacitor unless the press talk switch is used to send a signal, and the microphone output is never turned on even when a signal is being transmitted from the signal generator, preventing signal reception from the other party. The present invention provides an extremely effective microphone circuit for a transmitter that is extremely reliable and does not transmit inadvertent conversations near the microphone.

The details of the present invention will be explained below with reference to FIG. 2 showing an embodiment.

In Fig. 2, one end of the capacitor C is connected to the output side of the microphone M, and the other end is connected to the break contact b of the press talk switch Sp, and at the same time, the main contact a of the switch Sp is connected as a common circuit. Since the other end of capacitor C is normally connected to ground, the output of microphone M is bypassed by capacitor C, and the output of microphone M is prevented from being given to low frequency amplifier AA. ing. Also, when transmitting, the press talk switch Sp is operated, the main contact a switches to the make contact m, and the make contact m is connected to the transmitter control circuit CT, so the transmitter becomes operational and the capacitor C The end of the microphone is separated and the output of the microphone M is sent to the low frequency amplifier AA.

Therefore, unless the press talk switch Sp is operated, the output of the microphone M will not be sent out, and the transmitter start switch S
In response to signal transmission from signal generator SG by turning on s,
The output of microphone M is no longer superimposed as noise,
In addition, it is completely prevented that an unintentional conversation near the microphone M is transmitted without the user's knowledge, and it is possible to reliably avoid leakage of confidential information due to malfunction of the other party's signal receiver and inadvertent transmission of a conversation.

As the press talk switch Sp, in addition to a single-pole double-throw switch, individual make contacts and break contacts may be used, and in some cases, a similar circuit may be configured via a relay or the like.

Furthermore, ``In the above example, an FM transmitter and a dynamic microphone were used, but the same applies to AM, PM transmitters, etc., and the microphone M can also be used as long as it has an output regardless of the operation of the press talk switch. , even if a DC voltage is applied, it can be applied in the same way without any problem because it is bypassed by the capacitor C.As is clear from the above explanation, according to the present invention, unnecessary transmission of microphone output is possible with a simple circuit configuration. Since this is reliably prevented, there is no malfunction of the signal receiver on the other end, no leakage of security, etc., and great effects can be obtained when used in microphone circuits of various transmitters.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional example, and FIG. 2 is a block diagram showing an embodiment of the present invention. M...Microphone, C...Capacitor, S
p...Press talk switch, a...Main contact, b...Break contact, m...Make contact, CT...
...Transmitter control circuit. Figure 1 Figure 2

Claims (1)

[Claims] 1. In a microphone circuit in a simplex communication transmitter, a capacitor has one end connected to the output side of the microphone, and the other end of the capacitor is always connected to a common circuit to bypass the microphone output. A microphone circuit for a transmitter, characterized in that it is also provided with a pre-talk switch that disconnects the other end of the capacitor during transmission and controls each part of the transmitter to an operating state. 2. Claim No. 2, characterized in that the switch is used as a pre-talk switch, in which the main contact is connected to a common circuit, the break contact is connected to the other end of a capacitor, and the make contact is connected to a transmitter control circuit. A microphone circuit of the transmitter according to item 1.