JPS6331144B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a calling system for digital telephones in which voice signals and control signals are mutually exchanged by digital signals via an exchange.

Conventional analog telephone ringing systems do not supply power to the telephone when it is not in use, and when a call is made, the exchange sends out a large-amplitude AC ringing signal. It drove the calling circuit of the telephone. For this reason, the telephone circuit needs to be designed with high voltage resistance, which has drawbacks in hardware design such as not being suitable for future LSI conversion, and drawbacks such as requiring complex call signal generation and control functions in the switchboard. Ta.

Recently, digital telephones that mutually receive voice signals and control signals (dial signals, ringing signals, etc. transmitted between the telephone and the exchange when making and receiving calls) in the form of digital signals via the exchange have become popular.

In this digital telephone ringing system, the DC power that was conventionally supplied from the exchange after forming a loop during off-hook is also supplied during the ringing before off-hook, and a digitized ringing signal (calling code signal) is superimposed on the DC signal. It is preferable to make the call using In this case, the digital telephone that identifies the calling code signal and calls the called party needs to be supplied with power during the sending of the calling code signal before going off-hook. Regarding this, for example, as seen in Japanese Patent Application Laid-Open No. 54-163609, a temporary power supply trigger signal is sent from the exchange at the time of a call,
By detecting the power supply trigger signal in the digital telephone, the power supply circuit is started up, and the digitized call code signal sent from the exchange following the power supply trigger signal is identified, and the power supply to the digital telephone is maintained. Methods have been proposed. However, such methods (i)
Control procedures such as starting up the power supply circuit of the digital telephone and driving the calling circuit at the time of calling are complicated. (ii) Since transient phenomena such as the power supply trigger signal are used, there are problems such as a large impact on the stability of the rise and fall characteristics of the power supply trigger signal and the rise characteristics of the power supply circuit of the telephone. .

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to eliminate power consumption when the telephone is not in use, to require a high-voltage design of the telephone, and to provide a method using a simple procedure. To provide a calling system for a digital telephone that can stably start up a power supply circuit of a telephone and drive a calling circuit, and does not require maintenance work.

The details of the present invention will be explained below with reference to the drawings.

FIG. 1 shows an example of the circuit of a digital telephone used in an embodiment of the present invention, in which 1 and 2 are subscriber line terminals of the digital telephone, 3 is a switch, 4 is an electronic switch that closes when a call is made, and 5 is a power supply. circuit, 6 and 7 are diodes, 8 is a polarity reversal detection circuit, 9 is a polarity changeover switch, 10 is a switch linked to the switch, 11 is a power supply circuit that drives the electronic switch 4, 12 is a calling signal detection circuit,
13 is a calling circuit, 14 is an electronic switch that switches on/off power supply to the calling circuit, 15 is a calling speaker, 16 is the digital telephone circuit body excluding the calling/calling part, and 17 and 18 are diode bridge circuits. It is.

When the telephone user picks up the handset when making a call using the digital telephone shown in Figure 1, the switch 3
is closed to form a DC loop with the exchange via the subscriber path. Due to the formation of this DC loop, the power supply circuit 5 starts up, and at the same time, the exchange determines the formation of this DC loop and detects a call from the telephone.

At the time of a call, the exchange side inverts the polarity of the DC power supply supplied from the exchange as illustrated in the waveform diagram of FIG. That is, the potential of the line terminal 1 is changed from +V volts to -V volts with the line terminal 2 as a reference. As a result, the diode 7 of the polarity reversal detection circuit 8 becomes conductive, the power supply circuit 11 starts up, and the electronic switch 4 is closed. When the electronic switch 4 is closed, the power supply circuit 5, which forms a DC loop with the exchange via the subscriber line, starts up. When the power supply circuit 5 starts up, the digital telephone circuit main body 16 and the ringing signal detection circuit 12 operate. The calling signal detection circuit 12 detects the calling code signal 19 shown in FIG. 2, closes the electronic switch 14, and drives the calling circuit 13, thereby causing the speaker 15 to sound and informing the called party of the call.

By the way, if the subscriber line between the telephone and the exchange is temporarily connected with reverse polarity during line construction and the telephone is installed, the power supply voltage will reverse the polarity even though it is not a call, and diode 7 will become conductive. The power supply circuit 11 starts up, the electronic switch 4 closes, and the power supply circuit 5 starts up. As a result, the digital telephone circuit 16 and the ringing signal detection circuit 12 operate.
However, since it is not a regular call, the call code signal 19 is not sent from the exchange, and the call signal detection circuit 12 does not close the electronic switch 14, so the call circuit 13 is not activated. Since this state is not a standby state in which the digital telephone can determine whether it is a legitimate call, it is undesirable for the digital telephone to remain in this state even for a short time. Therefore, the calling signal detection circuit 12 determines that no calling code signal is sent, immediately switches the polarity changeover switch 9, and connects the power supply circuit 11 to the line terminal 2 via the diode 6 of the polarity detection circuit 8. do. diode 6
As a result of the connection, the power supply to the power supply circuit 11 is stopped, the electronic switch 4 is opened, and the power supply to the power supply circuit 5 is stopped. As a result, the digital telephone circuit main body 16 and the ring signal detection circuit 12 stop operating, and the digital telephone is kept in a standby state in which a normal call can be determined. Note that the polarity changeover switch 9 maintains the connection to the diode 6 by using a switch that is self-maintained even when no power is supplied.

In this state, when the polarity of the DC power supplied from the exchange is reversed at the time of a call, the potential of line terminal 1 changes from -V volts to +V volts with line terminal 2 as a reference, and diode 6 becomes conductive and the power supply Circuit 11 starts up. As a result, the electronic switch 4 is closed, the power supply circuit 5 is turned on, and the digital telephone circuit 16 and the ringing signal detection circuit 12 are activated.
Subsequently, since this is a regular call, a call code signal 19 is sent from the exchange. The calling signal detection circuit 12 detects that the calling code signal 19 has been sent, closes the electronic switch 14, and drives the calling circuit 13 to cause the speaker 15 to sound and notify the called party of the call. When the called party picks up the handset, the switch 3 closes.
At the same time, the switch 10 linked to the switch is opened, power supply to the power supply circuit 11 is stopped, and the electronic switch 4 is opened. Further, at the same time as the switch 3 is closed, the electronic switch 14 is opened to stop the power supply to the paging circuit 13, thereby stopping the operation of the paging circuit 13. Even if the electronic switch 4 is opened, the power switch 3 is closed, so the formation of the DC loop is maintained and communication is possible.

When the call is completed and the caller hangs up the handset, the switch 3 is opened and the DC loop is disconnected. At the same time, the exchange determines that the DC loop has been disconnected and restores the polarity of the DC power supplied from the exchange. Thereafter, by opening the switch 3, closing the switch 10, and opening the electronic switch 14, the digital telephone can again be kept in a standby state in which a legitimate call can be determined.

Due to the operation described above, the phone does not consume power when it is not in use, and the power supply voltage supplied from the exchange can be set low, which not only eliminates the need for a high voltage design for the phone, but also allows you to easily In addition to stably starting up the power supply circuit and driving the calling circuit of the digital telephone, it is possible to eliminate the need for maintenance work such as checking the polarity of subscriber lines.

As explained above, as a calling method for digital telephones, by using a method in which the polarity of the DC power supplied from the exchange is reversed at the time of a call, and a calling code signal is subsequently sent out, (i) the telephone is used; In this state, the phone consumes no power. (ii) Since the power supply voltage supplied from the exchange can be set low, it is no longer necessary to design the telephone with a high withstand voltage. (iii)
By a simple procedure, it is possible to stably start up the power supply circuit of a digital telephone and drive the calling circuit.
(iv) Even if polarity reversal occurs at times other than when making a call, such as when the subscriber line between the telephone and the exchange is connected to the opposite polarity during line construction or telephone installation, the digital telephone automatically switches and the digital telephone By maintaining the system in a standby state in which a regular call can be determined, there are advantages such as eliminating the need for maintenance work such as checking the polarity of subscriber lines.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a digital telephone used in an embodiment of the present invention, and FIG. 2 is a waveform diagram of an example of a calling signal to the telephone of FIG. 1, 2...Line terminal of digital telephone, 3...
...Hook switch, 4...Electronic switch that closes when a call is made, 5...Power supply circuit, 6, 7...Diode, 8...Polarity reversal detection circuit, 9...Polarity changeover switch, 10...Switch linked with the box switch, 11 . . . Power supply circuit for driving the electronic switch, 12 . . . Call signal detection circuit, 13 . . . Call circuit, 14 .
16...Digital telephone circuit main body, 17, 18
...Diode bridge circuit, 19...Call code signal.

Claims (1)

[Scope of Claims] 1. In a digital telephone that sends and receives voice signals and control signals via a switchboard using digital signals, when a call is made, the telephone is connected to the subscriber line by closing the DC power supply in the switchboard, the subscriber line, and the telephone switch in the telephone set. By forming a DC loop between the telephone line and the exchange, DC power is supplied to the telephone, and the exchange detects the formation of the DC loop to detect a call from the telephone, and when a call is made, the DC voltage supplied from the exchange is By reversing the polarity and forming the DC loop, DC power is supplied to the telephone, and the telephone detects the polarity reversal to start up the power supply circuit of the telephone, and the power is sent from the exchange following the polarity reversal. driving a calling circuit of the telephone by detecting the calling code signal in the telephone; and if the calling code signal is not detected in the telephone after the polarity reversal of the DC voltage, a circuit in the telephone forming the DC loop is closed; A calling method for a digital telephone, which is characterized in that the polarity of the terminal is switched to the opposite polarity, and the polarity state is maintained even if the power supply is subsequently stopped.