JPH02168760A - Transmission level adjustment device for telephone set - Google Patents

Abstract

PURPOSE:To facilitate the transmission signal level to be kept within the standard by discriminating whether a DTMF signal sent is a selection signal or a communication signal other than speech signal by means of a polarity inversion detection circuit of a telephone line and revising the level of the signal outputted from an amplifier. CONSTITUTION:A polarity detection circuit 30 is arranged between telephone lines L1, L2 and a diode bridge 10 to detect the polarity in the telephone lines L1, L2. Then signal relating to the polarity is fed to a signal control circuit 32. The signal control circuit 32 discriminates a DTMF signal depending on the polarity of the telephone line whether it is a selection signal or a communication signal other than a speech signal and gives a control signal to a DTMF dialer circuit 22. The DTMF dialer circuit 22 has a switching means for amplification factor in its inside and switches the amplification factor by using a control signal from the signal control circuit 32. Thus, it is very easy to regulate the DTMF signal within the standard.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a selection signal for dialing and a DTMF (Dual Tone Mul
The present invention relates to a transmission level adjustment device for a telephone that adjusts the transmission signal level in a telephone that transmits both tiFrequency and tiFrequency signals.

[Prior Art] In recent years, pushbutton type telephones have become widely used instead of dial type telephones. This bush type telephone uses a DTMF signal as a dialing signal for selecting a party to call. A telephone that uses this DTMF signal can normally use the DTMF signal as a signal for communications other than phone calls, and can perform data transmission and the like. That is, by operating the keypad I at a predetermined timing during a call, it is possible to enter the password manually, operate the answering machine, operate the home control system, and perform data communication.

In such bush type telephones that use TMF signals, standards are set by Ordinance of the Ministry of Posts and Telecommunications regarding the output power level of selection signals and signals used for communications other than telephone calls. That is, for the selection signal, the ninth
As shown in the diagram with diagonal lines, the signal level of the low group frequency is (-1, 8, 5 + 0.8L) decibels (
dBm) or more, (-6,5+0.8L) 68m or less,
-) It is specified that it should not exceed -3.5 dBm, and for high frequency signals (-16,0 + L) d
Bm or more, (-6,5+L) 68m or less, and -2,
It is specified that it should not exceed 5 dBm. On the other hand, for signals used for communications other than telephone calls, the range is indicated by diagonal lines in Figure 10, and the output power for signals with frequencies up to 4 kHz is the average level (-1, 5 + L).
It is stipulated that the distance is 68m or less and the maximum level does not exceed OdBm.

Here, L is the line transmission loss at 150QHz from the switching equipment of the first type telecommunications carrier to the connection point of the terminal equipment (telephone).

[Problems to be Solved by the Invention] As described above, standards regarding the output power level of the selection signal and signals used for communications other than telephone calls are different.

However, it is not practical to have two types of output power levels and switch between them, and conventionally this has been achieved with one level.

That is, the output power level of the selection signal and the communication signals other than the telephone call was adjusted so as to fall within the shaded range in FIG.

However, as is clear from FIG. 11, the range in which the levels of both the selection signal and communication signals other than calls fall within the standard is very narrow. For this reason, it is very difficult to adjust the signal level, and there is a problem in that the level of the DTMF signal, especially in communications other than telephone calls, often does not fall within the specified range.

This invention was made with the aim of solving the above-mentioned problems, and it is possible to automatically determine whether it is when a selection signal is being sent or when a communication signal other than a call is being sent (1+1), and to switch the transmission level. The purpose of the present invention is to provide a transmission level adjustment device for a telephone that is capable of adjusting the transmission level of a telephone.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a transmission level adjustment device for a telephone that transmits both DTMF signals, a selection signal for dialing and a signal for communications other than calls. a signal generation circuit that generates a DTMF signal of a predetermined frequency according to input data, an amplifier that amplifies the DTMF signal generated in this signal generation circuit, and a polarity detection circuit that detects the polarity state of the telephone line. and determining means for determining whether the DTMF signal to be transmitted is a dialing signal or a communication signal other than a call based on the polarity state;
means for changing the level of the signal output from the amplifier depending on the type of signal, the dialing signal is set to a predetermined first level, and the other communication signals are set to a predetermined second level.
It is characterized by transmitting at a level of .

[Operation] For example, data input by pressing buttons such as "1" and "2" on the keypad is input to a signal generation circuit, where it is converted into a DTMF signal of a predetermined frequency. This DTMF signal is then amplified to a predetermined level by an amplifier.

Here, in the present invention, the polarity reversal detection circuit of the telephone line detects the polarity reversal, and depending on this state, it is determined whether the transmitted DTMF signal is a selection signal or a communication signal other than a call. Then, in order to change the level of the signal output from the amplifier according to this determination result, the dialing signal is set to a predetermined first level.
level, and communication signals other than telephone calls can be transmitted at a predetermined second level. Therefore, it is very easy to keep the output signal levels of both signals within the standard.

[Embodiment] Hereinafter, a transmission level adjustment device for a telephone according to an embodiment of the present invention will be described based on the drawings.

As shown in FIG. 1, telephone lines LL and L2 are connected to a handset 14 via a diode bridge 10 and a communication circuit 12. As shown in FIG. Therefore, the signals input from the telephone lines L1, L2 are converted into voice by the handset 14, and the voice input from the handset 14 is sent to the telephone lines L1, L2 as electrical signals.

Further, a key bat 20 having a plurality of button buttons is connected to a DTMF dialer circuit 22.
The MF dialer circuit 22 generates a DTMF signal of a predetermined frequency corresponding to each button on the key bat 20. Then, this DTMF signal is transmitted to the telephone line L1. ．． Sent to L2.

Here, in this invention, a polarity detection circuit 30 is arranged between the telephone line LIL2 and the diode bridge 10, and in this polarity detection circuit 30, the telephone line LIL2
1. ．． Detect the polarity state at L2. A signal regarding this polarity is then supplied to the signal control circuit 32. The signal control circuit 32 controls the DTMF signal depending on the polarity state of the telephone line.
When a signal is transmitted, it is determined whether it is a selection signal or a communication signal other than a call, and the control signal is converted into DTMF according to the determination.
The signal is supplied to the dialer circuit 22.

The DTMF dialer circuit 22 has an amplification factor switching means therein, and the amplification factor is switched by a control signal from the signal control circuit 32. In other words, the DTM to be sent
The F signal is set to a high level when it is a selection signal, and set to a low level when it is a communication signal other than a call. Therefore, in the case of a selection signal, the signal level may be set as shown in FIG. 9, and in the case of a communication signal other than a telephone call, the signal level may be set as shown in FIG. 10.
It becomes very easy to keep the DTMF signal within the standard.

Next, the configuration of the DTMF dialer circuit 22 will be explained based on FIG. 2. The DTMF dialer circuit 22 outputs a DTMF signal of a predetermined frequency in response to pressing of a button on the key bat 20.

The oscillator 50 outputs a predetermined high frequency signal, which is input to a pair of frequency dividers 52a and 52b. Frequency divider 52a, 52
b divides the input high frequency signal by a predetermined period and outputs a pulse signal of a desired frequency. That is, frequency divider 5
Signals from the key bat 20 are inputted to the keys 2a and 52b via the key interface 54. Therefore, for example, when the "1" button on the key bat 20 is pressed, two signals of 697 Hz and 1209 Hz, which are defined by the standard as DTMF signals, are
It is necessary to output signals with different frequencies. For this reason,
The frequency dividers 52a and 52b perform frequency division at different periods to form signals of two frequencies.

That is, the frequency divider 52a performs frequency division on the low frequency side, and
b performs frequency division on the high frequency side. In this way, pulse signals of a predetermined frequency are input to the address counters 56a and 56b, and counting is performed in accordance with the manual pulses. and,
According to this count value, the sign ROM 58 a, 58
Read the data at the corresponding address in b. Normally, a sine wave is stored in the signs R, 0M 58a, 58b, and by reading and outputting the value stored at the corresponding address according to the count value of the address counters 56a, 56b, digital information about the sine wave can be obtained. A signal can be output. The digital signal of this sine wave is then converted into an analog signal by a DA converter (digital/analog) 60.

In this way, analog signals of two specific frequencies corresponding to the buttons on the key bat 20 are obtained, and these are adjusted to a predetermined signal level by the amplifier 62 and output as a DTMF signal.

Here, in the DTMF dialer circuit 22 according to the present invention, the amplifier 62 has two feedback resistors: a resistor R1 with a large resistance value and a resistor R2 with a small resistance value. The configuration is such that one of the resistors R1, R2 can be selected by the switch SWI.

Therefore, when the resistor R1 is selected in the switch SWI, the amplification factor in the amplifier 62 is set to a large value in proportion to this resistance value, and when the resistor R2 is selected, the amplification factor is set to a small value. be done. Therefore, in the case of a selection signal, the switch SWI selects the resistor R1 and outputs a predetermined high level DTMF signal, and in the case of a communication signal other than a call, the switch SWI selects the resistor R2 and outputs a predetermined high level DTMF signal. outputs a DTMF signal.

The switching of this switch SWl is performed by switch SW2.
The on/off of the switch SW2 is controlled by a control signal from the signal control circuit 32 which is manually inputted via the inter-7ace 64. Therefore,
Depending on the polarity state of the telephone lines LL and L2, the signal control circuit 32 determines whether the transmitted signal is a selection signal or a communication signal other than a call, and accordingly switches the switch SW.
2. SWI is controlled, and a DTMF signal at a predetermined signal level is output.

Next, the specific configuration of the polarity detection circuit 30 will be explained based on FIG. 3.

In the example shown in FIG. 3(A), telephone lines Ll, L
Two transistors 30 that turn on and off depending on the polarity of
It has 2,304. That is, Tora〉Jista 30
2.304 has a telephone line L1. ．． It is connected to L2 through predetermined resistors R3 and R4, its emitter is connected to ground, and its collector is connected to logic circuit 306.

Therefore, if the telephone line L1 is at a quality level, the transistor 304 is turned on, and the input terminal 30 of the logic circuit 306 is turned on.
8 is a low level. On the other hand, in this state, the telephone line L2 is at a low level, so the transistor 302 is off, and the input terminal 310 of the logic circuit 306 is at a high level. Note that the input terminals 308 and 310 of the logic circuit 306
is configured to be at a high level in an open state by, for example, being connected to a power supply via a resistor.

And telephone line L1. ．． When the polarity of L2 is inverted, the on/off states of the transistors 302 and 304 are inverted, and the input terminals 308 and 310 in the logic circuit 306 are inverted.
The levels at are also inverted.

Therefore, the logic circuit 306 can determine the polarity state of the telephone lines L1 and L2 by the levels of its input terminals 308 and 310. Therefore, a signal regarding this polarity state can be supplied to the signal control circuit 32.

FIG. 3(B) shows a phototransistor 320.
This is a polarity detection circuit 30 using H.322. That is,
In this example, a phototransistor 32 is connected to the telephone line L2.
0.322 light emitting elements DID2 are arranged in parallel. Since the current flow directions of the light emitting elements DI and D2 are opposite, one of the phototransistors 320 and 322 is turned on depending on the current flow state in the telephone line L2. , these ho1-
The h transistors DI, D2 are connected to two input terminals 308, 310 of the logic circuit, respectively.

Therefore, the logic circuit 306 can determine the polarity of the telephone lines L+, L2 in the same way as in the above case.

Next, we will discuss the polarity state of the telephone line at the time of transmission.
This will be explained based on the diagram. In other words, when not in use,
Telephone lines LL and L2 are in a constant polarity state. When making a call, the user picks up the receiver (off-hook) and operates the button on the keypad 20 to make a dial call. The dial signal in this dialing is sent to the exchange, and the exchange identifies the communication partner according to the dial signal, connects to the communication partner's line, and sends a calling signal thereto. In the state up to this point, the polarity of the telephone line does not change. Then, when the other party picks up the receiver, the polarity of the telephone line is reversed, and a call is made in this state.

The DTMF signal used for communications other than telephone calls is sent out in the call state, and the dial signal is sent out in the dial call state. Therefore, depending on the polarity state, it is possible to determine whether the signal is a dial call or a communication signal other than a call.

That is, the signal control circuit 32 determines whether the DTMF signal sent out according to the flowchart shown in FIG. 5 is a dial signal or a communication signal other than a telephone call.

First, the current polarity P1 is stored using a signal from the polarity detection circuit 30. The signal control circuit 32 is a DTMF
By controlling the switching means of the dialer circuit 22, the DTMF signal level is set to the high level side, that is, the switch SWI is set to the resistor R.
Set to the I side □, therefore, pick up the handset 14 1
) dialing in the low state will be done in the high state.

Next, it is detected whether or not the polarity has been reversed, and if the polarity has been reversed, the switch SWI in the DTMF control circuit 22 is switched to the resistor R1 side and to the resistor R2 side. As a result, the level of the DTMF signal to be sent out can be set to a predetermined low level. Therefore, the DTMF signal that is subsequently emitted during a call is sent at a low level within the standard, which is preferable for a DTMF signal for communication other than a call.

On the other hand, the polarity of the telephone line during reception is shown in Figure 6 (A).
, the state is as shown in (B).

That is, in an unused state, the telephone line Ll.

L2 is set to a particular polarity state P1. and,
When a telephone is identified by dialing on the transmitting side, a ringing signal is supplied from the exchange; upon reception of this ringing signal, the polarity of the telephone line is reversed, and a ringing tone is generated in this reversed state. Then, when receiving a call, by picking up the handset, both types of jammers are connected and a call is started;
By going off-hook), the polarity is reversed again, and a call is made with the polarity returned to its original state.

Furthermore, even if transmission is canceled on the transmitting side before going off-hook during reception, the polarity is inverted again as shown in FIG. 6(B).

Therefore, during reception, the signal control circuit 32 operates as shown in FIG.

That is, first, the characteristic P1 of the telephone line at that time is stored. If the dial is not dialed and the polarity is reversed, it is determined that reception is in progress, and then it is determined whether the handset has been picked up. Then, the transmission level of the DTMF signal is set to a low level only when the handset is picked up and the polarity returns to its original state.

In normal telephone operations, when the handset is lifted up, the polarity returns to its original state at the same time, but as shown in Figure 6 (B), when transmission is stopped, the polarity returns to its original state. In order to prevent the transmission level of the DTM F signal from being set to a low level when the telephone returns, it is determined whether the handset has been picked up. Since the transmission level of the DTMF signal in the telephone call state is set to a low level, the DTMF signal for communications other than telephone calls can be transmitted at a predetermined level.

Furthermore, what is shown in FIG. 8 is another embodiment of the switching means for switching the transmission level of the DTMF (M number).

That is, in this embodiment, the switch SW3 and the resistor R4 connected to ground are used. Therefore, when this switch SW3 is turned on, the DTMF signal transmission line is connected to the ground via the resistor R4. Therefore, the signal level of the transmitted DTMF signal is attenuated. Note that the degree of attenuation can be adjusted to a predetermined value by changing the ratio of the resistor R4 to the resistor R5 inserted into the sending signal line.

As described above, in the embodiment shown in FIG. 8, the level of the DTMF signal sent out can be changed by operating the switch SW3, and a selection signal for dialing and a communication signal other than a call having a desired signal level can be switched. can be sent.

Note that it is preferable to employ semiconductor elements such as transistors as the switches SWI to SW3.

[Effects of the Invention] As explained above, according to the transmission level adjustment device for a telephone according to the present invention, it is possible to determine whether the transmitted DTMF signal is a selection signal or a communication signal other than a call based on the state of polarity inversion. Since the signal level of the DTMF signal to be sent out is changed accordingly, the levels of the selection signal and communication signals other than calls can be easily kept within the standard.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of a transmission level adjustment device for a telephone according to the present invention, FIG. 2 is a block diagram showing the configuration of a DTMF dialer circuit 22 in the same embodiment, and FIG. A circuit diagram showing a configuration example of the polarity detection circuit 30 in the embodiment, FIG. 4 is an explanatory diagram for explaining the polarity state during transmission in the telephone, and FIG. 5 explains the operation of the signal control circuit 32 during transmission. FIG. 6 is an explanatory diagram for explaining the polarity state during reception, FIG. 7 is a flowchart for explaining the operation of the signal control circuit 32 during reception, and FIG. 8 is a DTMF dialer circuit. FIG. 9 is a characteristic diagram showing the standard of the DTMF signal used as a selection signal. FIG. 10 is a characteristic diagram showing the standard of the DTMF signal used for communications other than telephone calls. is a characteristic diagram showing an overlapping portion of both a selection signal and a communication signal other than a call. 30... Polarity detection circuit 32... Signal control circuit 22... DTMF dialer circuit 20... Key bat SWL~SW3... Switch

Claims (1)

[Claims] (1) A transmission level adjustment device for a telephone that transmits both DTMF signals, a selection signal for dialing and a signal for communications other than calls, and generates a DTMF signal of a predetermined frequency according to input data. A signal generation circuit, an amplifier that amplifies the DTMF signal generated in this signal generation circuit, a polarity detection circuit that detects the polarity state of the telephone line, and depending on the polarity state, whether the transmitted DTMF signal is a dialing signal or communication other than a call. a determining means for determining whether the dialing signal is a signal; and a means for changing the level of the signal output from the amplifier depending on the type of the transmitted DTMF signal, and setting the dialing signal to a predetermined first level;
A transmission level adjustment device for a telephone, characterized in that it transmits other communication signals at a predetermined second level.