JPS5931074Y2 - Audio switching circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an audio switching circuit in a citizen band transceiver (hereinafter referred to as a transceiver) attached to a radio receiver.

A transceiver that comes with a radio receiver can operate in three ways: transceiver operation, radio operation, and standby operation, which normally listens to the radio reception output and automatically switches to the transceiver reception output when there is a transceiver signal. Equipped with operational functions.

By the way, when such a transceiver is in standby mode, the modulation circuit is shared with the audio amplification circuit when transmitting, so it is necessary to stop the radio output, and when switching from transmitting to receiving, the transmitter's If the signal is delayed and the radio output comes out before the signal from the other party arrives, there is a possibility that the radio output may be mistaken for the other party's voice.
Since this becomes very difficult to hear, it is necessary to delay the radio output for a certain period of time.

In view of the above points, the present invention was devised to solve such problems and eliminate such drawbacks. It is possible to realize an audio switching circuit capable of blocking the radio reception output when switching from transmission to reception and delaying the radio reception output when switching from transmission to reception.
To provide an audio switching circuit which can set a characteristic that is good in terms of audibility and can prevent radio output from being output before a signal from a transmission partner arrives.

In order to achieve such an object, the present invention provides a switching element whose control electrode is connected to a squelch circuit of a transceiver receiving circuit through a first diode and is driven by the output of the squelch circuit to cut off the output of the radio receiving circuit. a means for controlling the conduction time of the switching element, which comprises a capacitor and a first resistor connected in parallel between the control electrode of the switching element and the ground; The switching element is connected to the transmission power supply circuit of the transceiver through a series circuit of resistors, and the switching element is driven by the output of the transmission power supply circuit during transmission of the transceiver.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the audio switching circuit according to the present invention.

In the figure, TCR is a transceiver receiving circuit, which includes a detection circuit DET that detects a signal from an input terminal IN to which an intermediate frequency signal is applied, a squelch circuit SQ whose input is the output of this detection circuit DET, and an output of a detection circuit DET. It is composed of a gate circuit G which is controlled by the output of the squelch circuit SQ as an input.

RR is a radio receiving circuit, TNC is a tone circuit which receives the output of the gate circuit G and the output of the radio receiving circuit RR through a resistor R1, and LA is a low frequency circuit which receives the output of the tone circuit TNC and the output of the microphone signal amplifier MA as inputs. Amplifier circuit, S
P is a speaker that amplifies the output of the low frequency amplification circuit LA.

Tr is a transistor constituting a switching element that cuts off the radio output; its collector is connected to the output terminal of the radio receiving circuit RR, its emitter is grounded, and its base is connected to the squelch circuit SQ through a diode D in the opposite direction. It is also grounded via a capacitor C and a resistor R2 in parallel.

Here, capacitor C and resistor R2 are transistor T
This was provided to control the conduction time of the

SWl and SW2 are interlocking transmission/reception changeover switches, and the transmission side terminal T of this transmission/reception changeover switch SW1 is connected to the low frequency amplifier circuit L.
It is connected to the transmission circuit TRC and the microphone signal amplification circuit MA, which input the output of
2 in series to the base of the transistor Tr, and the receiving terminal R is connected to the transceiver receiving circuit TCR.

Further, the movable contact of the transmission/reception changeover switch SW2 is connected to the microphone signal amplification circuit MA, and the transmission side terminal T of the fixed contact is connected to the low frequency amplification circuit LA.

SW3 is a function changeover switch, the movable contact is connected to the power source B, the fixed contact transceiver terminal TC is connected to the movable contact of the transmission/reception changeover switch SW1, the fixed contact radio terminal RO is connected to the radio reception circuit RR,
The standby terminal SB of the fixed contact is connected to the diode D3. D
4 in the forward direction, the transmission/reception changeover switch SW,
are respectively connected to the movable contacts of and the radio receiving circuit RR.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

First, when the function changeover switch SW3 is connected to the radio terminal RO, power is supplied to the radio reception circuit RR and it is in the radio reception state, and when it is connected to the transceiver terminal TC, the radio reception circuit RR is in the radio reception state. When power is supplied to the circuit TCR and the transceiver is in the operating state and connected to the standby terminal SB, power is supplied to the transceiver receiving circuit TCR and radio receiving circuit RR through diodes D3 and D4, and the radio and transceiver are activated. It enters a standby state with simultaneous operations.

Now, in the standby state, the transmission/reception changeover switch SW1 is connected to the reception side terminal R, and in the reception state, the intermediate frequency signal applied to the input terminal IN is detected by the detection circuit DET,
The detection output is supplied to squelch circuit SQ and gate circuit G.

When the detection output reaches a preset level, the squelch circuit SQ supplies an output to the gate circuit G and at the same time applies the output to the base of the transistor Tr through the diode D1.

Since the transistor Tr is turned on by the output of the squelch circuit SQ, the radio receiving circuit RR
The detection output of falls to ground through the transistor Tr,
The output that was being supplied to the tone circuit TNC through the resistor R1 is stopped.

On the other hand, when there is an output from the squelch circuit SQ, the gate circuit G becomes conductive, and the transceiver reception output passes through the tone circuit TNC, is amplified by the low frequency amplifier circuit LA, and is then sent to the speaker SP, where it can be heard. Become.

Next, the transmission/reception switching circuits SW1 and SW2 are connected to the transmission side terminal T, and when the transmission state is established, power is supplied to the microphone signal amplification circuit MA and the transmission circuit TRC, and the microphone input is amplified by the microphone signal amplification circuit MA. After that, it is further amplified by a low frequency amplification circuit LA, and its output is given to a transmission circuit TRC as a modulation signal.

Furthermore, this power is supplied to the transmitting circuit TRC and at the same time is supplied to the transistor Tr through the resistor R3 and the diode D2, and the transistor Tr becomes conductive, so that the output of the radio receiving circuit RR is supplied to the transistor Tr.
Since the voltage is grounded by the voltage, the output to the tone circuit TNC is cut off.

Next, when the transmission/reception selector switches SW and SW2 are connected to the reception side terminal H and enter the reception state, power is no longer supplied through the resistor R3 and the diode D2, but the electric charge stored in the capacitor C is transferred to the resistor R2 and the transistor. Since the transistor Tr is conductive until the discharge ends through the base-emitter of the Tr, the output of the radio receiving circuit RR is grounded and the tone circuit TNC is grounded.
It does not appear in

On the other hand, the transceiver receiving circuit TCR is supplied with power and starts operating, and when there is a received signal, the squelch circuit SQ is activated and the transceiver receiving circuit TCR is connected to the transistor T through the diode D.
r, the radio output from the radio receiving circuit RR is cut off, the gate circuit G is made conductive, and the output of the transceiver receiving circuit TCR is sent to the tone circuit TNC, thereby making it possible to listen to the transceiver signal.

In the above circuit configuration, by appropriately selecting the values of the capacitor C and the resistor R2, it is possible to determine the time period during which the transistor Tr is kept conductive, that is, the time period during which the radio output is delayed.

According to the results of experiments, it is appropriate to set this delay time within 0.5 seconds to 2 seconds.

As described above, according to this invention, an extremely simple circuit configuration can be used without the need for an extra switch circuit.
In a transceiver attached with a radio receiver, it is possible to realize an audio switching circuit capable of blocking the radio reception output during transmission and delaying the radio reception output when switching from transmission to reception.

In this embodiment, a transistor is used as a switching element for cutting off the radio output, but the present invention can of course be applied to a circuit using a field effect transistor, and an embodiment thereof is shown in FIG.

FIG. 2 is a circuit diagram showing another embodiment of the present invention.
In the figure, the same numbers as in Figure 1 indicate corresponding parts,
FET is a field effect transistor.

Here, the difference from FIG. 1 is that a field effect transistor FET is used as a switching element for cutting off radio output.

In this way, even when a field effect transistor FET is used, the conduction time of the field effect transistor PET can be controlled by appropriately selecting the values of the capacitor C and the resistor R2 connected between the gate electrode and the ground. can.

As explained above, according to the present invention, it is possible to cut off the radio reception output during transmission and delay the radio reception output when switching from transmission to reception with a simple circuit configuration without using an extra switch circuit. Since it is possible to realize a sound switching circuit that has good audibility, it is also possible to prevent the radio output from being output before the signal from the other party is received, so the practical effect is extremely low. It is.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the audio switching circuit according to the present invention, and FIG. 2 is a circuit diagram showing another embodiment of the present invention. TCR...Transceiver receiving circuit, RR...
...Radio receiving circuit, TNC...Tone circuit,
LA...Low frequency amplification circuit, SP...Speaker, MA...Microphone signal amplification circuit, TRC...
...Transmission circuit, D1-D4...Diode, Tr...Transistor, FET...
・Field effect transistor, C... capacitor,
R1-R3...Resistance, SWl, SW2...
...Transmission/reception selector switch, SW3...Function selector switch.

Claims (1)

[Scope of utility model registration request] In a transceiver attached to a radio receiver, a switching element whose control electrode is connected to a squelch circuit of a transceiver receiving circuit via a first diode and is driven by the output of the squelch circuit to cut off the output of the radio receiving circuit; means for controlling the conduction time of the switching element, which comprises a capacitor and a first resistor connected in parallel between the control electrode of the switching element and ground; 1. An audio switching circuit comprising: means connected to a transmission power supply circuit of a transceiver via a series circuit, and driving the switching element by an output of the transmission power supply circuit during transmission of the transceiver.