JPS584862B2 - Answering machine with signal discrimination function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal discrimination circuit capable of discriminating an audio signal from a continuous signal, an intermittent signal, or no signal.

Such a signal discrimination circuit is used, for example, as follows.

In other words, in the case of an answering machine, the above-mentioned device is kept in a continuous state of operation while the voice signal from the customer is continuously applied (this means, for example, without interrupting the voice signal for more than 10 seconds). When the customer finishes using the device and returns the handset, a continuous signal such as a dial tone or a busy tone will be heard, depending on the region. Either an intermittent signal is sent from the station to the device, or the input terminal on the device becomes a no-signal state.

However, the continuous signal or intermittent signal described above causes the audio switch circuit within the device to malfunction, making it impossible to restore the device to the standby state.

In order to prevent such malfunctions, there is a conventional method of using, for example, a filter circuit.

However, this method using a filter circuit has the disadvantage that there are many adjustment points and there are many malfunctions due to harmonics.

The present invention has been made in order to improve the above-mentioned drawbacks, and is easy to adjust, has a small number of parts, and is economical.If the operating point is set so that it operates reliably by voice signals, dialing sound, busy The object of the present invention is to provide a signal discrimination circuit that is not affected by the frequency and amplitude of sound.

Next, the present invention will be specifically explained with reference to a circuit diagram showing one embodiment.

FIG. 1 is a circuit example of the present invention, FIG. 2 is a truth table of a counter circuit, and FIG. 3 is an explanatory diagram of operations for voice signals and busy sounds.

First, in FIG. 1, numeral 1 denotes a rectifying and smoothing circuit, which envelopes a signal applied to an input terminal IN.

For this purpose, capacitor C2 is set to the required minimum value.

2 is a switching circuit, consisting of transistors Q1 and Q2.
is a Schmitt circuit that provides a signal with a steep fall to the counter circuit described later.

3 is a counter circuit, and SN7493 is used in the embodiment.

This can also be configured by combining 7490, 7492 or FF circuits.

4 is a first timer circuit using a multi-bye break circuit, and in the embodiment, a waveform as shown in C in FIG. 3 is obtained, and the output of Q5 is "H" for about 0.2 seconds, which is about 0.8 It is "L" for a second.

During this "H" period, the above-mentioned counter circuit is in a reset state, and during this "L" period, it is in a counting state.

5 is a second timer circuit, which repeatedly charges the timer capacitor C5 while the audio signal is being applied, and keeps the relay RY in the operating state while C5 is being charged, thereby maintaining the talking state of the telephone line. However, when there is a busy tone, dial tone, or no signal, the C5 stops charging, and then for example about 1
When the discharge of C5 ends after 0 seconds, relay RY is restored and works to return the device to the standby state.

Next, it will be described in more detail.

"When an audio signal is added" First, a process in which relay RY is maintained in an operating state by an audio signal will be explained.

Methods for maintaining communication between a customer and an answering machine while relay RY is maintained in operation are known.

Now, since the customer's voice signal is usually applied to the input terminal IN via an amplifier equipped with an ALC (automatic level control circuit), the level of the voice signal remains almost constant regardless of the distance from the telephone. can.

This audio signal is rectified by diodes D1 and D2, smoothed by capacitor C2, and then enveloped.

This DC output is waveform-shaped by a Schmitt circuit including transistors Q1 and Q2, and is further applied to transistor Q3.

Therefore, for example, if an audio signal as shown in diagram A in FIG. 3 is added and VL is the operating point of the Schmitt circuit described above, the collector voltage of Q3 becomes as shown in diagram B.

On the other hand, diagram C shows the output waveform of a multi-bye break circuit composed of transistors Q4 and Q5, for example, ta to t.
It is assumed that the time between b is about 0.8 seconds, and the time between tb and tc is about 0.2 seconds.

This time does not need to be exact. On the other hand, the counter circuit 3 using SN7493 is in a reset state when terminals 2 and 3 are "H", and is in a counting state when terminals are "H".
And in this counting state, the terminal 14 changes from "H" to "L".
There is a property that the count number changes to a base number at the time of switching to .

Diagrams B and C specifically illustrate this.

That is, for example, the period between ta and tb is the period in which the counting state is in effect, and within this period, the above-mentioned count number is advanced at the time point indicated by the arrow in diagram B.

That is, between ta and tb, the waveform in Figure B has a count of 4, but in the embodiment, the counter output is taken out from the C and D terminals as shown in the figure, so C in the truth table in Figure 2 is
As shown by the C and D outputs, when the count is 4 or more, the C and D outputs become "H".

Therefore, this output turns on the transistor Q6 and turns off the transistor Q7 through the diode D3 or D4.
When 7 is turned off, the resistor R14 (100Ω in the example)
, capacitor C5 (100uF
) can be rapidly charged to a predetermined voltage value (approximately 10V in the example).

The reason for this is that in the present invention, even if the resistance value of R14 is lowered, malfunctions will never occur.

In other words, there are various methods for signal discrimination circuits other than the filter circuit described above, and among them, when a busy sound (intermittent signal) described later is added, the above-mentioned R14 is applied at the time when this intermittent state is switched. There is a risk that the capacitor corresponding to C5 described above may be charged through the corresponding resistor, and it has been impossible to lower this resistance value.

On the other hand, in the method using the counter circuit of the present invention, the output of the counter circuit becomes completely zero even with an intermittent signal, as will be described later, so that the resistor R14 can be made low.

When the resistance value of R14 is lowered, the following features are obtained.

In other words, as will be described later, if there is no signal for 10 seconds, relay RY is restored and the device returns to standby mode, the customer may stop speaking for 8 seconds while talking about his business. During these 8 seconds, the discharge current of the capacitor C5 keeps the transistors Q8 and Q9 ON, and the load relay RY can be kept in the operating state, but during this period, the terminal voltage of C5 gradually decreases.

In this way, if the customer speaks the next item after about 8 seconds have elapsed, the first word will quickly charge C5 to about 10V as described above via R14, which has a low resistance value. After that, the relay RY can be reliably maintained in the operating state.

If the resistance value of R14 is large, the time constant of R14 x C5 will be large, and the charging voltage of C5 will not rise until the word is spoken 2 to 3 times, and the relay RY will be activated after the above 10 seconds have elapsed. There is a risk that the data may be restored incorrectly.

Although it is repeated, conventional signal discriminating circuits have such drawbacks.

Now, going back to the explanation, when the time between ta and tb in Figure C has passed, during the next time between tb and tc, the counter circuit is reset as described above, and each terminal of A-D becomes "L", and then the next time A new counting state occurs between tc and td, and during this period, a total of 5 counts are counted in the illustrated example, but as described above, when the count is 4 or more, an "H" output is obtained from the C and D terminals of the counter circuit, and the capacitor is Charge C5 and relay R
This allows Y to be kept in continuous operation.

According to observation, the amplitude of the audio signal changes in various ways, so it is possible to count 5 to 10 counts in 0.8 seconds in the above example.

"When a busy tone is added" Second, when the customer finishes using the device and returns the handset, the busy tone (intermittent signal) shown in Figure D is added to the input terminal IN. Explain the operation.

Therefore, the collector voltage of Q3 becomes as shown in diagram E.

On the other hand, if the outputs of the multivibrator circuits Q4 and Q5 have a time relationship as shown in diagram F, the count number of the counter path 3 is 1, as is clear from the above.

Therefore, as is clear from Fig. 2, the outputs of the C and D terminals are "L", and the capacitor C5 can no longer be charged, and transistors Q8 and Q9 are turned off after, for example, 10 seconds when the charge of C5 is discharged. Next load relay R
Restore Y.

It is easy and well known to return the telephone answering machine to the standby state when the relay RY is restored.

Even if the F diagram has a time relationship like the F' diagram, the count number is 1, and the count number is 0 as in the F'' diagram.

However, in any case, the outputs of the C and D terminals of the counter circuit 3 are "L", and the capacitor C5 is not charged.

Note that instead of the multivibrator circuit 4 described above, a monostable multicircuit that oscillates upon receiving a trigger when an input signal is applied or a CR circuit similar thereto can also be used as the first timer circuit.

If the amplitude of this intermittent signal is below the above-mentioned operating point VL, the collector voltage of transistor Q3 remains "H" and remains the same as the no-signal state described later, and the count number is 0.
It is not possible to charge capacitor C5.

"When a dial sound is added" Thirdly, the operation when a continuous signal such as a dial sound is added will be explained.

This operation explanatory diagram is not shown because it can be easily explained from the above-mentioned busy tone operation explanatory diagram.

For example, if diagram D is replaced with a continuous signal, the count number of counter circuit 3 becomes 1 at each point of time te and tg in diagram F, and as is clear from the above, capacitor C5 of the second timer circuit 2 cannot be charged. , relay RY may be restored, for example, approximately 10 seconds after the customer returns the handset.

"When there is no signal state" In this case, of course, there is no input to be counted, so the count output of the counter circuit 3 is 0, and the relay RY can be restored after about 10 seconds as described above.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to only the illustrated and described embodiment,
The present invention may be modified and implemented in various ways without changing the gist of the present invention.

For example, a rectifier and smoothing circuit may be installed after the switching circuit, a monostable multi-circuit may be used instead of a multi-vibrator circuit, a circuit made up of individual components may be integrated into an IC, or the capacitor C5 may be charged depending on the audio signal. Instead, it can be implemented with various modifications, such as charging when a signal such as a busy tone is added.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, FIG. 2 is a truth table, and FIG. 3 is an operation explanatory diagram.

Claims (1)

[Claims] 1. A switching circuit that receives as input a voice signal, a continuous signal such as a dial tone, and an intermittent signal such as a busy tone; a counter circuit that uses the output of the switching circuit as a count input; and the counter. A first timer circuit is configured to control the circuit so that the operation of setting the circuit in a reset state for t1 seconds and in a counting state for t2 seconds is repeated as one cycle, and to charge the circuit when the signal input during the 12 seconds is at least the count number n or more. a second timer circuit in which the signal input during the 12 seconds is a signal whose count number is much smaller than the n, for example, a continuous signal other than an audio signal;
1. An answering machine having a signal discriminating function, comprising means for restoring the device by time-off of the second timer when there is an intermittent signal or no signal.