JPS62203449A - Telephone set - Google Patents

Abstract

PURPOSE:To attain the pleasant conference talking by constituting the 1st and 2nd balance means decreasing the bypassing of a transmission signal to a reception signal so as to be selected depending on the state, thereby keeping the side tone to a nearly constant optimum sound volume in the conventional talking state and the conference talking state. CONSTITUTION:A reception signal from the 2nd telephone line is sent to the secondary winding 8c coupled electromagnetically from a winding 8b, extracted from a connecting point between impedance circuit networks 16, 17 and fed to the receiver of a handset, from which the signal is listened to, sent to a trunk line winding 8a and given also to the 1st telephone line. Since the 5th contact 7e of a conference talking switch is closed, an impedance circuit network 16b is connected in parallel with an impedance circuit network 16a. Since two telephone lines having equal impedance are connected in parallel in terms of AC, the impedance of the telephone line of the secondary side of the low frequency transformer 8 is lowered nearly 1/2, the side tone attenuation is kept to an optimum value and the talking is attained similarly as at the conventional talking.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a telephone capable of making conference calls to which two or more telephone lines are connected simultaneously.

BACKGROUND OF THE INVENTION In recent years, there has been an increase in the number of telephones that can connect two or more 7rL communication lines to one telephone. Some of these telephones first use one telephone line to make a call to the other party;
There are telephones that can then use the other telephone line to call a second party, allowing three people including the party to talk at the same time (so-called conference call).

Hereinafter, a conventional telephone conference call circuit as described above will be explained with reference to the drawings.

FIG. 2 shows the configuration of the main parts of a conventional telephone capable of making conference calls. In FIG. 2, 1 and 2 are connection terminals to the first telephone line, and 3 and 4 are connection terminals to the second telephone line. 5 is a first telephone line selection switch that is operated when making a call to the first telephone line;
It has two contacts 5a and 5b. Reference numeral 6 denotes a second telephone line selection switch that is operated when making a call to the second telephone line, and has two contacts 6as (3b), and is connected to the first telephone line selection switch 5 and the machine (contract agreement). 7 is linked to the first one and is configured to operate reciprocally.
This is a conference call switch that is operated when three parties are talking at the same time: the other party on the second telephone line, the other party on the second telephone line, and the party on the device.It has four contacts 7a-7b%7.
It is composed of c s 7 d. Reference numeral 8 denotes a low frequency transformer, which includes a winding 8a connected to the first telephone line, a winding 8b connected to the second telephone line, and a secondary winding 8.
It is composed of c. 9 is a bridge diode, 10
11 is a dial signal sending circuit for sending a dial signal to a telephone line; 11 is a telephone circuit network consisting of a dial button (not shown) and a control circuit connected to the dial signal sending circuit 10; 12 is a transistor; and 13 is a Zener diode. , 14 is a bias resistor connected between the collector and base of the transistor 12, 15 is a coupling capacitor, and 16, 17, and 18 are impedances /, Zl, Z
2, Z3 is an impedance network. 19 is an input terminal for a transmitting signal, 20 is an output terminal for a receiving signal, and 21 is a common terminal. Further, 22 is a hook switch, and when the handset (not shown) is lifted up, contacts 22a and 22b are activated.
is configured so that it is in the on state. Also, 25.2
Reference numeral 6 designates switches that are operated to put the first and second telephone lines on hold, respectively, and resistors 23 and 24 are connected to the respective telephone lines.

Regarding telephones configured as above that can make conference calls,
The operation will be explained below.

First, the case of making a call to the first telephone line will be explained. When the first telephone line selection switch 5 is operated, its contacts 5a and 5b close. If you lift the handset (not shown), the contacts 22a' and 22 of the hook switch 22 will open.
b is in the on state, and the current of the first telephone line flows through the contact 22b1 of the hook switch 22, the bridge diode 9, the dial signal sending circuit 10. It flows to the telephone network 11 via the power supply switch 1' 14. Part of the current also flows through the Zener diode 13 and generates a constant voltage (approximately 5V), which becomes the operating voltage of the telephone network 11. When a dial button (not shown) is operated, the dial signal sending means 1o cuts off the line current and sends a dial pulse to the first telephone line. Once connected to the other party, a telephone call can be made using a handset (not shown) connected to the telephone network 11. Here, the operation of the side sound protection circuit composed of the transistor 12 and the impedance circuit networks 16 to 18 will be explained. Transistor 12 is now in operation because its base is biased by resistor 14.

When a transmitting signal is applied to one transmitting signal input terminal from a transmitter of a handset (not shown), an output signal appears at the collector of the transistor 12, and the secondary winding 8c of the low frequency transformer 8 is transmitted to the central line side. 218b, and a transmit signal is transmitted to the first telephone line. Further, the reception signal from the first telephone line is transmitted from the office line side winding 8b of the low frequency transformer 8 to the secondary side winding 8c, and the impedance network 16 and 17
The signal is taken out from the connection point of , and applied to the receiver of a handset (not shown) so that it can be listened to. On the other hand, the looping of the transmitted signal to the received signal (so-called sidetone) has the following relationship: Z1 + Z2 = ZL: Z3, where ZL is the impedance when looking at the telephone line from the secondary side of the low frequency transformer. It becomes zero when the formula holds true. Therefore, the circuit constants constituting the impedance circuit networks 16 to 18 should satisfy the above relational expression (actually, the impedance of the telephone line changes depending on the line condition, so the amount of sidetone attenuation that can be satisfied within this range is set as desired).

Here, a case will be described in which the first telephone line is put on hold and another person is called through the second telephone line to make a conversation. First, the first telephone line is placed on hold. When the first hold switch 25 is operated to close the contact, the resistor 23 is connected to the telephone line.

Next, when the second telephone line selection switch 6 is operated, the contacts 5a of the first telephone line selection switch 5,
5b is opened and the telephone network 11 etc. are disconnected from the first telephone line. However, since the resistor 14 is connected, the first telephone line will not be disconnected. Further, the contacts 6a and 6b of the second telephone line selection switch 6 are turned on, and since the handset remains lifted, the hook switch 22 is turned on, so that the second telephone line is closed. The current in the second telephone line is hook switch 2
2 contacts 22b1 bridge diode 9, dial signal sending circuit 10. The signal flows to the telephone network 11 via the power selector switch 14.

Part of the current also flows through the Zener diode 13 and generates a constant voltage (approximately 5V), which is applied to the telephone network 1.
The operating voltage is 1. When a dial button (not shown) is operated, the dial signal sending means 10 cuts off the line current and sends a dial pulse to the second telephone line. Once connected to the other party, a telephone call can be made using a handset (not shown). Next, a case where three people talk to the other parties on the first and second telephone lines (so-called conference call) will be explained. When the conference call switch 7 is operated, the contacts 78 to 7d are turned on, and the winding 8a of the low frequency transformer 8 is connected to the first telephone line, the winding 8b is connected to the second telephone line, and the winding 8c is connected to the telephone line. Connected to network 11 and also contacts 25 and 26 of the hold switch
is opened, the resistors 23 and 24 are disconnected from the TL telephone line, and the current of each telephone line flows through the windings 8a and 8b of the low frequency transformer 8 to maintain the closed state. On the other hand, the voltage (approximately 5 V) generated between the terminals of the Zener diode 13 is applied to the telephone circuit network 11.\, and current for operation is supplied. When a transmitting signal is applied to the transmitting signal input terminal 19 from the transmitter of the handset (not shown), an output signal appears at the collector of the transistor 12, and from the secondary winding 8C of the low frequency transformer 8 to the station winding. 8a and 8b, and transmit signals are sent to the first and second i-talk lines. Also, the reception signal from the first 7rL telephone line is a low frequency I.
It is transmitted from the office line side winding 8a of the lance 8 to the secondary side winding 8c, taken out from the connection point of the impedance network 16 and 17, applied to the receiver of a handset (not shown) for listening, and further transmitted to the office line side winding. 8b and is also transmitted to the second telephone line. The incoming signal from the IT telephone line of 'f%2 is transmitted from the winding 8b to the electromagnetically coupled secondary winding 8c, taken out from the connection point between the impedance networks 16 and 17, and sent to the handset (not shown). The signal is applied to the telephone receiver and can be heard, and is further transmitted to the office line side winding 8a and also transmitted to the first telephone line. are transmitted to the second telephone line and the telephone network 11, respectively. A conference call can be made as described above.

Problems to be Solved by the Invention However, with the above configuration, during a conference call, the impedance seen from the secondary side of the low frequency transformer is such that two telephone lines are connected, so it is difficult to communicate with only a single telephone line. The volume of the sidetone has decreased (reduced to about 1/2) compared to when the sound is active, deviates greatly from the above relational expression, and the volume of the sidetone increases.

As a result, the user's own voice becomes louder and louder, making it difficult for the user to speak.For this reason, the user tends to speak in a low voice, reducing the volume transmitted to the other party. Another problem is that when the handset is placed face down on a desk or placed next to a wall, ringing may occur due to side noise.

The present invention has been made in view of the above-mentioned conventional technology, and it maintains the sidetone at a nearly constant optimal volume in a call state with only one telephone line (normal call) and in a conference call state, making it difficult to talk. To provide a telephone that allows comfortable conference calls without causing noise or ringing.

Means for Solving the Problems In order to achieve this object, the telephone of the present invention includes first and second balancing means for reducing the wraparound of the transmitted signal into the received signal, and a single telephone line. switch means for switching between a first state in which the telephone line is connected to the telephone line and a second state in which the telephone line is connected to the plurality of telephone lines, and when the switch means is in the first state, the first balance means is selected. , second
In the talking state, the second balance means is selected.

Effect: Due to this configuration, the balance means can be switched between a call with only one telephone line (normal call) and a conference call, thereby keeping the sidetone at a nearly constant optimum volume.
Also, no more noise is generated.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of the main parts of a telephone capable of making conference calls according to this embodiment. In Fig. 1, 1 and 2 are connection terminals to the first telephone line, 3 and 4 are connection terminals to the second telephone line, and 5 is the connection terminal when talking to the first 7rL telephone line. This is the first telephone line selection switch to be operated, and has two contacts 5a and 5b. 6 is a second telephone line selection switch that is operated when making a call to the second telephone line, and has two contacts 6 a z 6 b, and is connected to the first telephone line selection switch 5 and the machine. They are structured so that they are linked to each other and operate reciprocally. Reference numeral 7 denotes a conference call switch that is operated when three parties are talking at the same time, including the other party on the first telephone line, the other party on the second telephone line, and the party on the device, and has five contacts 7as, 7b, and 7e%.
It is composed of 7ds 7e. Reference numeral 8 denotes a low frequency transformer, which includes a winding 8 a connected to the first telephone line, a winding 8 b connected to the second telephone line, and a secondary winding 8
It is composed of c. 9 is a bridge diode, IO
11 is a dialing signal sending circuit for sending a dialing signal to a telephone line; 11 is a telephone circuit network consisting of a dial button (not shown) and a control circuit connected to the dialing signal sending circuit 10; 12 is a transistor; and 13 is a Zener diode. , 14 is a bias resistor connected between the collector and base of the transistor 12, 15 is a coupling capacitor, and 16a116b, 17.18 is an impedance network whose impedances are Z1, Zl, Z2, and Z3, respectively. 19 is an input terminal for a transmitting signal, 20 is an output terminal for a receiving signal, and 21 is a common terminal. Further, 22 is a hook switch which is configured so that when a handset (not shown) is lifted up, contacts 22a and 22b are turned on. Further, 25 and 26 are switches that are operated when holding the first and second TL lines, respectively, and resistors 23 and 24
are connected to each 71f telephone line.

Regarding telephones configured as above that can make conference calls,
The operation will be explained below.

First, the case of making a call to the first telephone line will be explained. When the first telephone line selection switch 5 is operated, its contacts 5a and 5b close. Here, when you lift the handset (not shown), the contacts 22a122b of the hook switch 22
is turned on, and the current of the first telephone line flows through the contact 22b1 of the hook switch 22, the bridge diode 9, the dial signal sending circuit 10, and the power changeover switch 14 to the telephone circuit network 11. Part of the current also flows through the Zener diode 13 and generates a constant voltage (approximately 5V), which becomes the operating voltage of the telephone network 11. When a dial button (not shown) is operated, the dial signal sending means 10 cuts off the line current and sends a dial pulse to the first telephone line. When connected to the other party, the telephone circuit network 11
A telephone call can be made using a handset (not shown) connected to the terminal. Here, the operation of the side sound protection circuit composed of the transistor 12 and the impedance circuit networks 16 to 18 will be explained. Transistor 12 is now operative because it is biased to its base by resistor 14. When a transmitting signal is applied to the transmitting signal input terminal 19 from the transmitter of the handset (not shown), the output signal is transmitted to the transistor 12.
appears at the collector of the low frequency transformer 8, and the secondary winding 8c of the low frequency transformer 8
The signal is transmitted to the office line side winding 8b, and a transmission signal is sent to the first telephone line. In addition, the reception signal from the first telephone line is transmitted from the office line side winding sb of the low frequency transformer 8 to the secondary side winding 8.
The signal is transmitted to C, taken out from the connection point between impedance networks 16 and 17, and applied to the receiver of a handset (not shown) so that it can be heard. On the other hand, if the impedance when looking at the telephone line from the secondary side of the low frequency transformer is ZL, the looping of the transmitted signal to the received signal (so-called sidetone) is
・Z2=ZL: Z3 becomes zero when the relational expression (1) is established. Therefore, the circuit constants forming the impedance circuits wJ16 to wJ18 should satisfy the above relational expression (actually, the impedance of the telephone line changes depending on the line condition, so the amount of sidetone attenuation that can be satisfied within that range is be used exclusively).

Here, a case will be described in which the first telephone line is put on hold and another person is called through the second telephone line to make a conversation. First, the first telephone line is put on hold. When the first hold switch 25 is operated to close the contact, the resistor 23 is connected to the telephone line.

Next, when the second telephone line selection switch 6 is operated, the contacts 5a of the first telephone line selection switch 5,
5b is opened and the telephone network 11 etc. are disconnected from the first telephone line. However, since the resistor 23 is connected, the first telephone line will not be disconnected. Also, the contact 6a16b of the second telephone line selection switch 6 is turned on, and since the handset remains lifted, the hook switch 22 is turned on, so that the second telephone line is closed. The current in the second telephone line is hook switch 2
The signal flows to the telephone network 11 via the bridge diode 9, the dial signal sending circuit 10, and the power changeover switch 14.

Part of the current also flows through the Zener diode 13 and generates a constant voltage (approximately 5V), which is applied to the telephone network 1.
The operating voltage is 1. When a dial button (not shown) is operated, the dial signal sending means 10 cuts off the line current and sends a dial pulse to the second telephone line. Once connected to the other party, a telephone call can be made using a handset (not shown). Next, a case where three people talk to the other parties on the first and second telephone lines (so-called conference call) will be explained. When the conference call switch 7 is operated, each of the contacts 7a to 7d and 7e is turned on, and the winding 8a of the low frequency transformer 8 is connected to the first telephone line, the winding 8b is connected to the second telephone line, and the winding 8c is connected to the first telephone line. is connected to the telephone network 11. Also, contact 2 of the hold switch
5 and 26 are opened, the resistors 23 and 24 are disconnected from the telephone line, respectively, and the current of each telephone line flows into the windings 8a and 8b of the low frequency transformer 8 to maintain the closed state.

On the other hand, a voltage (approximately 5.V) generated between the terminals of the Zener diode 13 is applied to the telephone circuit W411, and current for operation is supplied. When a transmitting signal is applied to the transmitting signal input terminal 19 from the transmitter of the handset (not shown), an output signal appears at the collector of the transistor 12, and from the secondary winding 8C of the low frequency transformer 8 to the station winding. 8as
8b, and a transmitting signal is sent to the eleventh second telephone line. Further, the reception signal from the first telephone line is transmitted from the office line side winding 8a of the low frequency transformer 8 to the secondary side winding 8c, taken out from the connection point between the impedance networks 16 and 17, and sent to the handset (not shown). The signal is applied to the telephone receiver and can be heard, and is further transmitted to the office line side winding 8b and also transmitted to the second telephone line. The reception signal from the second telephone line is transmitted from the winding 8b to the electromagnetically coupled secondary winding 8c, taken out from the connection point between the impedance networks 16 and 17, and applied to the receiver of the handset (not shown). The signal can be heard and heard, and is further transmitted to the central office line side winding M8a, and is also transmitted to the first TL telephone line. Also, since the fifth contact 7e of the conference call switch is turned on, the impedance network 16
b is connected in parallel to impedance network 16a.

For this reason, circuits with approximately equal impedance (Zl) are connected in parallel, so the combined impedance is approximately 0.521.
becomes. Therefore, the above relational expression (1) is 0.521: Z2=ZLa: Z3 (2
), and the impedance of the line that provides the optimum amount of sidetone attenuation in this state is ZLa=0.5(Zl-23/Z2) (3) from equation (2). On the other hand, from formula (1), ZL=(Zl・Z 3/Z 2 ) (4
'), so ZLa-0,52L (5), and the optimum amount of sidetone attenuation can be obtained when the impedance of the telephone line seen from the secondary side of the low frequency transformer 8 is reduced to 1/2. Become. On the other hand, during a conference call, two telephone lines with approximately equal impedance are connected in parallel in AC terms, so the impedance of the telephone line seen from the secondary side of the low frequency transformer 8 is approximately halved. It is declining.

For this reason, the amount of sidetone attenuation is maintained at an optimum level, and you can talk just like you would during a normal phone call. A conference call can be made as described above.

Effects of the Invention As described above, the present invention provides first and second balance means for reducing the leakage of the transmitted signal to the received signal, and a first state in which the telephone line is connected to a single telephone line. switch means for switching between a second state, which is a state of connection with a plurality of telephone lines;
Since the balance means is selected and the second balance means is selected in the second call state,
The balance method switches between a call with only one telephone line (normal call) and a conference call, and the sidetone can be kept at a nearly constant optimal volume, so it does not become difficult to speak or cause ringing. You can have comfortable conference calls without having to do anything.

[Brief explanation of drawings]

The first factor is a circuit diagram showing the main parts of a telephone capable of making conference calls according to the present invention, and FIG. 2 is a circuit diagram showing the main parts of a conventional telephone. 1.2 - Connection terminal to the first telephone line 3.4 - Connection terminal to the second telephone line "-11111 First telephone line selection switch 6 ----
---Second field telephone line selection switch 7-----Makoto Ichikai call switch 8---Low frequency transformer 9---Bridge diode 10--Dial signal sending circuit 11-- --- Telephone network 12 --- Transistor 13 --- Zener diode 14.23.24 --- Resistor 15 --- Capacitor 16a, 16b, 17.18 --- Impedance network 19 --- Input terminal 20 for one sending signal --- Output terminal 21 for one receiving signal --- Common terminal 22 --- Hook switch

Claims (1)

[Claims] A first balance means for reducing the looping of the transmitting signal to the receiving signal when connected to a single telephone line, and the looping of the transmitting signal to the receiving signal when connected to a plurality of telephone lines. a second balance means for reducing congestion; and a switch means for switching between a first state in which the telephone line is connected to a single telephone line and a second state in which the telephone line is connected to a plurality of telephone lines; A telephone set characterized in that the first balance means is selected when the switch means is in a first state, and the second balance means is selected when the switch means is in a second talking state.