JPS6325740B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an interface circuit, and more particularly to an interface circuit that can output earth air when power is cut off.

Generally, in a telephone communication network, a telephone 1 is connected to a desired transmission line by a repeater 4 via an exchange 2 and a terminal equipment 3, respectively, as shown in FIG. In this case, many control signals in the exchange 2, the terminal equipment 3, etc. use the open/ground interface. For example, when interfacing telephone dialing signals at the terminal equipment 3,
As shown in FIGS. 1 and 2, there is a method of interfacing with signal lines called SS/SR lines.

In other words, dialing signals etc. are transmitted to exchange 2.
Data is transmitted and received between the SR trunk (or SS SR trunk) 2a and the signaling processing section 3a of the terminal equipment 3, and from the signaling processing section 3a to the SR trunk 2a, the switch SW ₁ shown in FIG. 2 is turned on or off. The SR signal is sent by. Similarly,
As shown in FIGS. 1 and 2, an SS signal is sent from the SR trunk 2a to the signaling processing section 3a by turning on or off the switch _SW2 . When the switch SW ₁ is on, air is sent to the relay 5 in the SR trunk 2a, one end of which is connected to the -48V central office power supply, and activates it. It is determined that it is inside and is not accessed. Similarly, switch
When SW ₂ is on, the signaling processing unit 3a
Earth air is sent to relay 6, one end of which is connected to the -48V station power supply, to operate it.

Mechanical relays have conventionally been used as the switches SW ₁ and SW ₂ , and the power-off state of the mechanical relays has been defined depending on the type. In other words, if a normally-off type mechanical relay is used as the mechanical relay, it will be open when the power is turned off.On the other hand, if a normally-on type is used, which is turned off when the power is turned on, it will be open when the power is turned off. will be sent out from the earth. In this way, when a mechanical relay was used, it was possible to cope with a power outage.

However, in recent years, there has been a trend to use switching transistors (so-called electronic relays) as SW ₁ and SW ₂ for the purpose of compactness, high reliability, and low cost. Sometimes, the drawback was that its behavior could not be specified.

An object of the present invention is to provide an interface circuit that minimizes the number of elements and can send out earth air with low power consumption when the power is turned off, especially in a terminal device that uses an electronic relay as an SR signal output switch. It is in.

The present invention provides SS/SR communication between the exchange and the terminal equipment.
In a circuit that interfaces with a wire, one or more diodes each have one end connected to the base of one or more transistors used independently as an SR signal sending switch, and the other end of the diode is connected to the base of one or more transistors. The above disadvantages are eliminated by constructing an interface circuit with a single switch that is turned on when the power is turned off and forward biases this diode. explain.

FIG. 3 shows a circuit diagram of a first embodiment of the interface circuit according to the present invention. This embodiment and a second embodiment to be described later will be described using a case where a PCM24B is used as the terminal equipment. PCM24B is 1
The system has 24 channels, and each system has its own power supply. Additionally, control is basically system independent. Therefore, for example, when performing SR earth air transmission when the power is cut off, the failure signal from the power panel will cause the 24
It is necessary to send earth air to all SR lines for the channel.

In FIG. 3, Q ₁ , Q ₂ , ..., Q ₂₄ are switching NPN transistors (corresponding to SW ₁ in FIG. 2) in the signaling processing section 3a, and CH1
The emitter is connected to the SR line of each channel shown as SR, CH2SR, ..., CH24SR, and the collector is grounded. Further, the bases of the transistors _Q1 to _Q24 are connected to dialing signal input terminals ₇₁ to ₇₂₄ via current sources _I1 to _I24 .

In this embodiment, the cathodes of the diodes D _{1 to D 24 are connected to the bases of the transistors Q 1 to Q 24 separately ,} and the anodes of the diodes D ₁ to D ₂₄ are connected to the bases of the transistors Q 1 to Q 24.
It is configured to be connected to a switch 8 that is turned on when the power is turned off.

In Figure 3, when power is normally supplied, switch 8 is off and the diode
Since the anodes of D ₁ to _{D 24} are respectively open, the transistors Q ₁ to _{Q 24} operate independently according to the binary dialing signals inputted to their bases from the input terminals 7 ₁ to 7 ₂₄ . From that emi ivy
Outputs the SR signal to the SR line.

On the other hand, if the power supply (this is the power obtained by dividing the voltage from the station power supply of the terminal equipment, so there is no need to consider cutting off the station power supply itself here) is cut off for some reason, the switch 8 is turned on, the anodes of diodes D ₁ to _{D 24} are grounded via switch 8, and these are biased in the forward direction. As a result, base current flows through the bases of Q ₁ to _{Q 24} via diodes D ₁ to _{D 24} , and earth air can be sent out from each emitter of Q ₁ to _{Q 24} . Here, the transistor
If the current amplification factors of Q ₁ to _{Q 24} are respectively β, the current flowing through the switch 8 is only 1/β of the sum of the SR line currents, so a switch 8 with a small current capacity can be used.

FIG. 4 shows a circuit diagram of a second embodiment of the circuit of the invention. In the figure, Q ₁ ′ to Q ₂₄ ′ are switching PNP transistors for sending out SR signals, and their emitters are grounded and their collectors are connected to the SR lines of the respective channels indicated by CH1SR to CH24SR. Also 9 ₁ ~
9 ₂₄ is a dialing signal input terminal, which is connected to transistors Q ₁ ′ through level shifters 10 ₁ through 10 ₂₄ .
Connected to the base of Q ₂₄ ′. In the circuit with the above configuration, in this embodiment, the anodes of the diodes D ₁ ′ to D ₂₄ ′ are connected to the bases of the transistors Q ₁ ′ to _{Q 24} ′, respectively, and the cathodes of the diodes D ₁ ′ to _{D 24} ′ are connected to the resistors R A switch 11 that is turned on when the power is cut off via
It is connected to one end of the . The other end of the switch 11 is connected to the -48V office power supply of the terminal equipment.

In this embodiment, as in the first embodiment, the switch 11 is turned off during normal operation, so that the transistors Q ₁ ′ to Q ₂₄ ′ receive binary dialing signals input to the input terminals 9 ₁ to 9 ₂₄ . Switching operations are performed independently of each other depending on the conditions. For example, transistor Q ₁ ′~
The base of Q ₂₄ ′ has - depending on the dialing signal.
When 2V or +1V is applied and -2V, Q ₁ ′ ~
Q ₂₄ ′ is on, and when +1V, Q ₁ ′ to Q ₂₄ ′ are off.

On the other hand, when the power is turned off, the switch 11 is turned on, and the power is transferred from the bases of the transistors Q ₁ ′ to _{Q 24} ′ through the forward biased diodes D ₁ ′ to _{D 24} ′, the resistor R, and the switch 11. Current flows. Therefore, in this embodiment, as in the first embodiment, the transistors Q ₁ ′ to Q ₂₄ ′ are respectively turned on.
Earthly air is sent to the SR line. Also transistor
If the current amplification factors of Q ₁ ′ to _{Q 24} ′ are β′, then a current that is β′ times the base current of each of Q ₁ ′ to _{Q 24} ′ flows through the SR line of each channel.
A current of 1/β' of the total SR line current flows through.

In addition, in PCM24B terminal equipment, etc.
There is already a ground air interface contact that outputs power failure information to the power supply panel, and this ground air interface contact may be used as the switch SW.

As described above, according to the present invention, one end of a diode is connected to the base of a transistor used independently as an SR signal sending switch, and the other end of the diode is connected in common, so that a single switch that is turned on when the power is turned off is connected. Since it is configured to be connected to the switch, it is possible to send out earth air from the collector or emitter of the transistor when the power is turned off.Also, since it sends out earth air, there is no need to provide a separate power supply, and all that is required is the addition of a diode. It can be configured at low cost, and even when the power is cut off, the current amplification effect of the transistor can be effectively used, and the current flowing through a single switch is reduced to SR.
It only requires 1/β of the total line current (β is the current amplification factor),
Therefore, an inexpensive switch with a small current capacity can be used as the switch.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a schematic configuration of a telephone communication network, FIG. 2 is a circuit diagram showing an example of a general interface circuit, and FIGS. 3 and 4 are diagrams showing respective embodiments of the circuit of the present invention. FIG. 2... Switchboard, 3... Terminal equipment, 5, 6... Relay,
7 ₁ to 7 ₂₄ , 9 ₁ to 9 ₂₄ ... dialing signal input terminal, 8, 11 ... switch, Q ₁ to Q ₂₄ ... NPN transistor for switching, Q ₁ ′ to _{Q 24} ′ ... PNP transistor for switching, D ₁ 〜D ₂₄ ，D ₁ ′〜D ₂₄ ′…
diode.

Claims (1)

[Claims] 1 In a circuit that interfaces an exchange and a terminal equipment with an SS/SR line, one end of each is connected to the base of one or more switching transistors that are used independently as switches for sending out SR signals. one or more diodes,
A single switch is commonly connected to the other end of the diode and is turned on to forward bias the diode when the power is off, and is connected to the emitter or collector of the transistor when the power is off.
An interface circuit characterized by sending earth air to the SR line.