JPS60227536A - Line-engagement detecting circuit - Google Patents

Abstract

PURPOSE:To compare the output of a level measuring circuit with a set comparison voltage and to prevent erroneous detection of busy caused by noise, by making variable and automatically setting the comparison voltage from the output level of the level measuring circuit over a long period of time. CONSTITUTION:The output of a transmitter 1 is inputted in the rectifier/smoothing circuit 9 of a level measuring circuit 2 and the output rectified and smoothed at the circuit 9 is inputted in a buffer amplifier 13 through a resistance 10. The output of the amplifier 13 is divided into two parts and one part is supplied to the input to be compared of a comparator circuit 15 and the other part is inputted in an integration circuit 17 through an opposite-polarity diode 16. The comparison voltage of the comparator circuit 15 is automatically changed and set from the output level of the level measuring circuit 2 over a long period of time. The set comparison voltage is compared with the output of the measuring circuit 2 at the comparator circuit 15 and erroneous detection of a busy-back tone due to noises near the transmitter 1 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to wireless devices. In particular, in transceivers, etc., this is related to a busy detection circuit that detects whether or not a call is busy and suppresses the transmission output. Conventionally, in transceivers that operate on batteries, the battery life is limited. Reducing power consumption has become an important issue in order to expand the market. For this reason, a method is known in which the power consumption in the transmitter is reduced by detecting whether or not the device is "busy" and stopping the transmission output when the device is not "busy."

Conventionally, as a method for detecting whether a call is "busy" or not, the amplitude level (envelope) of the audio signal from the transmitter is 1!
: A known method is to measure and compare whether the amplitude level is above or below a certain fixed value. However, in this method, since the input voltage from the transmitter increases in a place with large indoor noise, it may be determined that the call is "busy" due to indoor noise in addition to the speaker's voice. When this false detection occurs, the recipient has the inconvenience of hearing only noise intermittently, and if the detection value is increased, small voices cannot be detected, and the transmitted sound sometimes stops, etc. It has the following disadvantages.

The present invention improves this point, and provides a busy detection circuit that can make the level of the "busy" detection setting value variable according to fluctuations in the noise level, and has fewer false positives in "busy" detection. The purpose is to

The present invention increases the detection level when the noise level is high when it is not "busy" to avoid false detection due to room noise, and conversely, when the noise level is low, it detects even small voices. To provide a busy detection circuit that lowers the level.

The present invention provides a level measuring circuit that rectifies and smoothes input fg@ from a telephone transmitter and outputs the resultant signal, a circuit that automatically sets a comparison voltage variably based on the output level of this level measuring circuit over a long period of time, and The present invention is characterized by comprising a comparison circuit that compares the voltage with the output of the level measurement circuit and sends out a detection output.

An embodiment of the present invention will be described based on the drawings.

FIG. 1 is a diagram showing the main circuit configuration of an embodiment of the present invention. The output of the transmitter 1 is connected to a diode 5.6 via a DC cut capacitor 3 in a level measuring circuit 2. Commutator ff#1g formed by capacitor 7 and resistor 8
Connected to 1@9. The output of the rectifying and smoothing circuit 9 is led to the positive-phase input of the buffer amplifier 13 via the output resistance lO. Further, a bypass capacitor 14 is connected to this positive phase input. This buffer amplifier 1
The output of No. 3 is led to the compared input of the comparison circuit 15.

Further, the output of this buffer amplifier 513 is led to an integrating circuit 17 via a diode 16 of opposite polarity. This integrating circuit is formed by a resistor 18 and a capacitor 19,
Its integral output is connected to the comparison input of the comparison circuit 15.

FIG. 2 1i is an operation time chart showing the voltage waveform at the points indicated by X marks in FIG. 1. In FIG. 2, T8 indicates the busy time.

With such a circuit configuration, input 1g, v1n, from the transmitter
becomes a voltage vL proportional to its amplitude by the level measuring circuit 2. That is, in the level measurement circuit 2, the DC component is cut by the capacitor 3, rectified and smoothed by the diode 5, 6, capacitor 7, and resistor 8, and the fluctuation component is further suppressed by the resistor lO and the capacitor 14, and the voltage vL is output. . Of this output voltage vL, the minimum value vLmin when not in a "busy" state is a voltage indicating room noise.

On the other hand, the time constant determined by the resistor 18 and capacitor 19 button of the integrating circuit 17 is set to be sufficiently larger than the "busy" time Ts. For this reason, the comparison voltage vc applied to the compared input of the comparison circuit t5 when it is not "busy" is VC=vLm1n+VD (where VD is the conduction voltage of the diode]-6).

In this state, it becomes "busy" and the input 1 is turned to vxN.
As the amplitude of increases, the level measurement circuit 2
The output voltage VL of is also increased. When this output voltage VL exceeds the comparison voltage vc, the output voltage of the comparison circuit 15 is V.

It is detected that UT has woken up and is currently talking.

As explained above, according to the present invention, it is possible to configure the comparison voltage vc when detecting a "busy" state to automatically become 7% lower than the room noise by a certain voltage.

Therefore, even when indoor noise is high, a "busy" state is not erroneously detected, and it is possible to prevent only noise from being sent to the receiving side. Furthermore, since the constant voltage can be set as low as the conduction voltage of a diode, the comparison voltage can be lowered compared to conventional devices. Therefore, it is possible to accurately detect whether the speaker is "busy" due to the low voice of the speaker, the sensitivity of the microphone can be increased, and the performance of the transmitting device can be improved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of essential parts showing an embodiment of the circuit of the present invention. Figure 2 is an operation time chart showing the voltage waveform at the point indicated by the X mark in Figure 1. 1... Transmitter, 2... Level side V circuit, 3, 7.1
4.19... Capacitor, 5.6.16... Diode, 8, l0117... Resistor, 9... Rectifier and smoothing circuit, 13... Buffer amplifier, 15... Comparison circuit.

Claims (1)

[Claims] (1) A level measurement circuit that smooths the input signal from the transmitter and outputs it, a circuit that automatically sets a comparison voltage variably depending on the output level of this level measurement circuit over a long period of time, and this comparison voltage. and a comparison circuit that compares the output of the level measurement circuit with the output of the level measurement circuit and sends out a detection output.