JP2899320B2 - Telephone terminal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Industrial application field) The present invention relates to a telephone terminal in which a plurality of terminals are branch-connected to the same line.

(Prior Art) Conventionally, in the case where a plurality of standard telephones are used by branching and connecting to the same office line, the following operation is performed when a call with the office line is transferred to another telephone. Is performed. First, a call is put on hold by the telephone that is currently talking, and then a call is made to the user of the other telephone by any method (for example, by calling directly). As the other telephone picks up the telephone line in response to the call, the telephone line voltage drops. The transfer source telephone detects this drop in line voltage and releases the hold and line capture states. Thus, the transfer is completed.

(Problems to be Solved by the Invention) The problem with the conventional telephone described above is that if the handset is raised by another telephone while the call is on hold, the transfer is automatically performed even if there is no intention to transfer. It is in.

Therefore, an object of the present invention is to provide a case where a plurality of telephone terminals are connected to the same line by branch connection and transfer is performed only when a prescribed operation is performed on a telephone terminal during a call, and The purpose of the present invention is to prevent the transfer from being performed without permission by the operation of the telephone terminal.

[Configuration of the invention]

(Means for Solving the Problems) The present invention relates to a calling means for making a call to another telephone terminal in a state where the telephone line is seized in a telephone terminal branch-connected to another telephone terminal together with the telephone line. Call response detecting means for detecting that another telephone terminal has seized the telephone line in response to the operation of the calling means, and only when the line response of the other telephone terminal is detected by the call response detecting means. And a means for canceling the line capturing state of the own terminal. In a preferred embodiment,
Calling of another telephone terminal by the calling means can be performed only while the call is on hold.

(Operation) When the telephone terminal of the present invention is branch-connected to the same telephone line together with another telephone terminal, the telephone terminal responds to a call made from itself to another telephone terminal after the line is captured. Only when another telephone terminal has seized the line, the line seizing state of the own terminal is automatically released, and the transfer is completed.

(Example) Hereinafter, an example will be described.

FIG. 1 shows an overall configuration of a preferred embodiment of a telephone terminal according to the present invention.

This standard telephone is connected to a telephone line (not shown) such as a central office via line connection terminals L1 and L2. An AC terminal of a rectifier circuit 3 is connected to the line connection terminals L1 and L2 via a DC cut capacitor 1, and a ring tone generating circuit 5 is connected to the DC terminal of the rectifier circuit 3. When the call comes
A ringing signal of 16 Hz is sent from the telephone line, and is input to the ring tone generating circuit 5 through the capacitor 1 and the rectifier circuit 3. The ring tone generating circuit 5 drives the sounder 7 to generate a ringing tone.

An AC terminal of another rectifier circuit 13 is connected to the line connection terminals L1 and L2, and an internal communication line 17 of the telephone is connected to a DC terminal of the rectifier circuit 13 via a line switch 15. Line switch 15 is connected to internal communication line 17 and rectifier circuit.
13 and the transistor Tr1
and a transistor Tr2 for driving r1, which is closed by turning on the hook switch 21 when the handset 19 is off-hook and seizes the telephone line, and under the control of the central processing controller 11 when dialing in dial pulse mode. It is driven by a certain line control circuit 23 to transmit dial pulses to a telephone line.

The internal communication line 17 is a transmission signal output terminal 25 of the communication circuit 25.
In addition to being connected to a, it is also connected to the receiving signal input terminal 25b of the communication circuit 25 via the side tone prevention circuit 31. The receiver 27 and the transmitter 29 of the handset 19 are connected to a reception signal output terminal 25c and a transmission signal input terminal 25d of the communication circuit 25, respectively. Further, the output terminals of the MF signal generation circuit 33 and the hold tone generation circuit 35 are both
Connected to 25e.

In the communication circuit 25, a reception switch 37 and a transmission switch 41 are provided. The receiving switch 37
The voice signal from the receiving signal input terminal 25a given to the A contact or the MF signal input terminal 25e given to the B contact
Is sent to the input terminal of the receiving main amplifier 39. The output signal of the reception main amplifier 39 is transmitted to the receiver 27. The transmission changeover switch 41 is provided with either an audio signal from the transmission signal input terminal 25d supplied to the A contact and transmitted through the transmission preamplifier 43 or an audio signal supplied from the MF signal input terminal supplied to the B contact. One is sent to the input terminal of the transmission main amplifier 45. Transmission main amplifier
The output signal of 45 is sent to the internal communication line 17 through the output transistor Tr3. The changeover switches 37 and 41 are controlled by the central processing unit 11 via the transmission / reception switch control circuit 47, and are normally placed on the A contact side as shown in the figure, but the MF signal generation circuit 33 or the hold tone generation circuit 35 Is driven by the central processing unit 11, it is switched to the B contact side.

The reception main amplifier 39 can switch the gain between a normal gain and a large gain (for example, a value 6 dB larger than the normal gain), and the switching control is performed by the central processing unit 11 via the reception volume control circuit 49.

The internal communication line 17 is also connected to a transfer pulse generating transistor Tr4 and a branch detection circuit 51.
These are used to transfer from this telephone to any other telephone when this telephone and one or more other similar telephones are branch connected to the same telephone line. That is, at the time of transfer, the central processing unit 11 transmits the transfer pulse generation transistor Tr4 via the transfer pulse generation circuit 53.
To transmit a transfer pulse code of a predetermined number of bits (for example, 8 bits) for calling the transfer destination telephone to the telephone line three times as shown in FIG. 2 (in this case,
An activation pulse is also transmitted prior to the transfer pulse code). A unique 8-bit code is preset in each of the telephones connected in a branch, and when transferring to a certain telephone, the unique code of the telephone is transmitted to the telephone line as a transfer pulse code. Become. For this purpose, a memory (not shown) in the central processing unit 11 stores the unique codes of all the other telephones. The transfer pulse code transmitted to the telephone line is received by each telephone, and only the telephone whose transfer pulse code matches the unique code, that is, only the transfer destination telephone, sounds a ringing tone.
When the transfer destination telephone seizes the telephone line in response to this call, a decrease in the line voltage due to the telephone line is detected.
And sends a detection signal to the central processing unit 11.

A transfer call detection circuit 61 is connected to the line connection terminals L1 and L2 via a capacitor 55 and a step-up transformer 57. The capacitor 55 and the step-up transformer 57 have the function of a bandpass filter, and the pass band is adjusted to the frequency (for example, 28 KHz) of the transfer pulse which is much higher than the frequency of the audio signal (0.3 to 3.4 kHz) as shown in FIG. It is. These circuits are used in a branch connection to detect a transfer pulse code when a transfer is made from another telephone to this telephone. That is, the start pulse and the transfer pulse output from another telephone are input to the transfer detection circuit 61 through the capacitor 55 and the step-up transformer 57. In the transfer call detection circuit 61, the transfer pulse waveform shaping circuit 63 first shapes the input signal into a rectangular pulse having a specified logic level, and the data window circuit 67 responds only to a pulse having a pulse width equal to or smaller than the specified width ( That is, a rectangular pulse is generated (in response only to a pulse recognized as data). This data window circuit
67 has a first one-shot multivibrator 93 having a relatively large time constant and a second one-shot multivibrator 95 having a relatively small time constant. As shown in FIG. 4, the first one-shot multivibrator 93 is triggered by the rising edge of the square pulse A from the waveform shaping circuit 63 and outputs a square pulse B having a specified width. Triggered by the falling edge of the square pulse A, it outputs a narrow rectangular pulse B, and these output pulses B and C are input to the AND circuit 97. If the rectangular pulse A from the waveform shaping circuit 63 is equal to or smaller than the specified width, the rectangular pulse C is output within the output period of the rectangular pulse B.
Is also output, the rectangular pulse D having the same shape as the rectangular pulse C is output.
Is output from the AND circuit 97, and the rectangular pulse D is input to the central processing unit 11.

The central processing unit 11 activates the register 67 and the comparison circuit 69 in response to the first rectangular pulse, that is, the activation pulse. As a result, the subsequent train of rectangular pulses, that is, the transfer pulse code, is stored in the 8-bit register 65, and is input to the comparison circuit 69, where the telephone-specific information is preset by, for example, a dip switch (or a memory) 71. It is compared with an 8-bit code. This comparison process is performed for each of the transfer pulse codes transmitted three times repeatedly,
When a match result of two or more times is obtained, the comparison circuit 69 sends a transfer call detection signal to the central processing unit 11. Upon receiving this, the central processing unit 11 sends the buzzer 81
To generate a transfer ring tone.

Central processing unit 11 receives a logic signal indicating on-hook / off-hook of handset 19 from transistor Tr5 driven by hook switch 73. Further, the central processing unit 11 receives a signal indicating a pressed key from the keypad 75 through the key recognition circuit 77. Keypad 75 has
Dial key 75a, hold key 75b, receiving volume switch key 75c
Etc. are provided.

When the dial key 75a is pressed while the handset 19 is off-hook, the central processing unit 11 drives the line switch 15 in the dial pulse mode to generate a dial pulse, and the switch in the MF dial mode. 37 and 41 are switched to the B contact side and the MF signal generating circuit 33 is driven to generate an MF signal. The selection between the dial pulse mode and the MF dial mode is made in the central processing unit 11 in advance.

When the hold key 75b is pressed in the off-hook state, the central processing unit 11 switches the changeover switches 37 and 41 to the B contact side and drives the hold sound generation circuit 35 to generate a hold sound signal, thereby making a call. On hold. When an identification number (for example, "1") of another telephone is input from the dial key 75a during call holding, the central processing unit 11 reads a transfer pulse code from a memory area (not shown) corresponding to the identification number. This is sent to the telephone line through the transistor Tr4. The central processing unit 11 controls the branch detection circuit 51 only when the call is on hold and after the transmission pulse code is transmitted.
When the detection signal is output from the switch, the hold sound generation circuit 35 is stopped, the changeover switches 37 and 41 are returned to the A contact side, and the line switch 15 is released to return the telephone to the incoming call waiting state.

When the reception volume switching key 75c is pressed in the off-hook state, the central processing unit 11 switches the gain of the reception main amplifier 39 from the normal gain to the large gain.

This telephone device has two power supplies, one is a power supply circuit 83 connected to the internal communication line 17, and the other is a battery.
85, the output terminal of the power supply circuit 83 and the output terminal of the battery 85 are coupled via diodes 82 and 84 to supply a constant DC voltage VDD to each unit in the telephone. The power supply circuit 85 forms the main power supply of the telephone, and operates by receiving power from the telephone line only when the telephone line is seized. On the other hand, the battery 85 is an auxiliary power supply when the power supply circuit 83 is not operating. Supply the power required for memory backup.

The output voltage VBAT of the battery 85 is input to the voltage detection circuit 87. In the voltage detection circuit 87, only the output voltage VBAT equal to or higher than the specified voltage passes through the Zener diode 89 to turn on the transistor Tr6, thereby forming a logic signal indicating whether the output voltage VBAT is equal to or higher than the specified voltage. This logic signal is input to the central processing unit 11, and the central processing unit 11
Is a warning sound generation circuit when the output voltage VBAT is lower than the specified voltage.
1 is driven to output a predetermined warning sound from the buzzer 81.

FIG. 5 shows the configuration of the branch detection circuit. The voltage of the internal communication line 17, that is, the voltage of the telephone line (line voltage) is applied to a charging / discharging circuit having a relatively small time constant composed of a resistor 99 and a capacitor 101. The line voltage is also
And to the capacitor 105 through the reverse current blocking diode 103. The capacitor 105 is connected in parallel with the resistor 107 to form a discharge circuit having a relatively large time constant.
A series connection of a diode 109 and a resistor 111 is connected in parallel to the capacitor 101, and the diode 109 and the resistor 111 are connected in series.
Are connected to the gate of the PNP transistor Tr7. The emitter of the transistor Tr7 is connected to the positive terminal of the capacitor 107, and the collector is grounded through the voltage dividing resistors 113 and 115. And the NP with the emitter grounded
The gate of the N-transistor Tr8 is connected to the interconnection point of the voltage-dividing resistors 113 and 115, and the voltage of the collector is sent to the central processing unit 11 as an output signal of the branch detection circuit 51.

As shown in FIG. 6, when the line voltage E decreases stepwise due to the line capture of another telephone, the charging voltage of the capacitor 101 having a small discharge time constant, that is, the gate potential F of the transistor Tr7 rapidly decreases. On the other hand, the charging voltage G of the capacitor 101 having a large discharge time constant, that is, the transistor T
The emitter potential G of r7 decreases slowly. Therefore, the transistor Tr7 is turned on due to an increase in the gate-emitter voltage. As a result, the transistor Tr8 is turned on, and a low-level detection signal is output to the central treatment device 11.

Next, an operation in the case where a plurality of such telephones are branch-connected to the same telephone line and a call is transferred from a telephone during a call to another telephone waiting for an incoming call will be described.

When the hold key 75b is pressed on the telephone during a call,
The changeover switches 37 and 41 are switched to the contact side, and the hold sound generation circuit 35 outputs a hold sound signal. In addition, a flag indicating “pending” is set in the central processing unit 11. The hold tone signal is transmitted to the telephone line through the communication circuit 25 and the internal communication line 17. In this hold state, dial keys
When the identification number (for example, “1”) of the transfer destination telephone is input from 75a, the transfer pulse code corresponding to the identification number “1” is read from the memory in the central processing unit 11. Then, the start pulse and then the transfer pulse code are repeated three times, sent to the pulse generation circuit 53, and applied to the transistor Tr4. Thus, a pulse train as shown in FIG. 2 is transmitted to the telephone line. Simultaneously with the transmission of the transfer pulse code, a flag indicating that the transfer pulse code has been transmitted is set in the central processing unit 11.

At the transfer destination telephone, the hold tone is cut off by the capacitor 55 and the transformer 57, and only the above-mentioned pulse train is input to the transfer call detection circuit 61. The pulse input to the circuit 61 is shaped into a rectangular pulse having a prescribed logic level and sent to the central processing unit 11. The central processing unit 11 starts operating in response to the first pulse, that is, the starting pulse,
The register 67 and the comparison circuit 69 are activated. Followed by 3
The transfer pulse code transmitted repeatedly is input to the register 67 and the comparison circuit 69 each time, and is compared with the setting code of the dip switch 71. If the transfer pulse code matches twice or more, the transfer call detection signal is sent to the central processing unit 11. Is output. As a result, the transfer call generating circuit 79 is driven, and the buzzer 81 generates a ringing sound at the time of transfer.

Thereafter, when the handset 19 is raised at the transfer destination telephone, the line switch 15 closes to capture the telephone line. As a result, a state occurs in which the two telephones have seized the telephone line, and the line voltage decreases stepwise.

At the transfer source telephone, a drop in the line voltage is detected by the branch detection circuit 51, and the detection signal is sent to the central processing unit.
Output to 11. When the detection signal is input, the central processing unit 11 refers to the flags indicating the status of holding and after the transmission of the transfer pulse code. When both flags are on, the line switch 15 is opened, the generation of the hold tone is stopped, the changeover switches 37 and 41 are returned to the A contact side, and the transfer source telephone returns to the incoming call waiting state. At the same time, both flags are cleared. Thus, the transfer is completed.

If at least one of the flags is not set when the detection signal is output from the branch detection circuit 51, the hold release and the line capture release operations are not performed. Therefore, if the transfer pulse code is not transmitted even if the telephone is on hold, the transfer is not automatically performed even if another telephone goes off-hook.

The preferred embodiment of the present invention has been described above, but the present invention is not limited to this embodiment. For example, the signal for calling the transfer destination need not be a pulse code as in the embodiment, but may be another type of signal such as an MF signal. The ringing tone of the transfer destination may be such that a holding tone is output from the speaker instead of ringing a special ringing tone as in the embodiment.

〔The invention's effect〕

As described above, the telephone terminal according to the present invention responds to a call made from itself to another terminal when the terminal is branch-connected to the same telephone line together with another telephone terminal. Since it is configured to release its own line capture state only when another terminal captures the line, automatic transfer is not performed unless a call is made, that is, unless transfer is intended. Moreover, according to the present invention, smooth transfer can be completed with a minimum necessary transfer act.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of a telephone terminal according to the present invention, FIG. 2 is a diagram showing a transfer pulse code output from the telephone of FIG. 1, and FIG. 3 is a transfer pulse. FIG. 4 shows the comparison between the frequency of the audio signal and the frequency of the audio signal.
FIG. 5 is a waveform diagram for explaining the operation of the data window circuit in FIG. 5, FIG. 5 is a circuit diagram of the branch detection circuit in FIG. 1,
FIG. 6 is a waveform chart for explaining the operation of the branch detection circuit of FIG. 11 Central processing unit, 15 Line switch, 19 Handset, 23 Line control circuit, 35 Hold tone generation circuit, 51 Branch detection circuit, 53 Transfer pulse generation circuit , 55 …… Capacitor, 57 …… Step-up transformer, 61
…… Transfer ring detection circuit, 79 …… Transfer ring tone generation circuit, 81
……buzzer.

──────────────────────────────────────────────────続 き Continued on the front page (73) Patent holder 999999999 Meisei Electric Co., Ltd. 2-57-7 Koishikawa, Bunkyo-ku, Tokyo (72) Inventor Masanori Tanaka 3-1-1 Asahigaoka, Hino-shi, Tokyo Toshiba Corporation Inside the Hino Plant (72) Inventor Kazuhiro Izuka 3-1-1 Asahigaoka, Hino City, Tokyo Inside the Toshiba Hino Plant (72) Inventor Kenzo Masuoka 1-6-1 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Makoto Shimizu Nippon Telegraph and Telephone Corporation, 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo (72) Inventor Kimitoshi Nakamura 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation ( 72) Inventor Eiji Morikami 1-41 Kugayama, Suginami-ku, Tokyo Iwasaki Communication Equipment Co., Ltd. (72) Inventor Yuichiro Mitsutake 1-41 Kugayama, Suginami-ku, Kyoto Iwasaki Tsushinki Co., Ltd. (72) Inventor Tetsuya Imabori 2-23-2 Nishigotanda, Shinagawa-ku, Tokyo Kanda Communication Industry Co., Ltd. (72) Inventor Yasushi Mori Tokyo 2-23-2 Nishi-Gotanda, Shinagawa-ku, Kanda Communication Industry Co., Ltd. (72) Inventor Takahisa Arai 2-57-7 Koishikawa, Bunkyo-ku, Tokyo Meisei Electric Co., Ltd. 2-5-7 Koishikawa, Bunkyo-ku Meisei Electric Co., Ltd. (56) References JP-A-61-174859 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04M 1 / 00,1 / 72

Claims (2)

(57) [Claims] In a telephone terminal branch-connected to another telephone terminal together with another telephone terminal, calling means for making a call to the other telephone terminal in a state where the telephone line is captured, and operation of the calling means. Call response detecting means for detecting that the other telephone terminal has seized the telephone line in response to the call, and only when the line response of the other telephone terminal is detected by the call response detecting means, Means for canceling the line capture state of the telephone terminal. 2. The telephone terminal according to claim 1, further comprising means for holding a call, wherein said calling means calls said another telephone terminal only when the call is on hold.