JPS6214159B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to trunk circuits for automatic telephone exchanges.

A trunk circuit of a conventional automatic telephone exchange will be explained with reference to FIG. 1, which shows the main parts of an example of a loop dial type trunk circuit of a crossbar exchange and an electronic exchange. In Figure 1, relay J is for detecting an incoming signal from the opposing station, and relay D is for detecting a response signal from the opposing station when this trunk makes a call, in other words, a call line polarity reversal signal. It is constructed with a polarized relay that can operate even with a minute current, so that it can be moved even if the line resistance between the lines is large. These organic relays D and J are inserted and connected between the communication lines even during a call in order to monitor the state of the game. Therefore, if the communication current flows through these polarized relays D and J, it will also deteriorate the communication quality, so in order to reduce the loss of these communication currents, a communication current is connected in series with the polarized relays D and J. Line ring RPT0 and
RPT1 is inserted and connected. When this trunk receives a call from the opposing station, a loop is formed between the LA line and the LB line as the incoming signal from the opposing station.
1st winding of RPT1 - Break contact e of relay E
- LB wire - Game loop - LA wire - Break contact a of relay A - Break contact b of relay B - Break contact e of relay E - 2nd winding of wire ring RPT1 -
Second wire winding of polarized relay J - battery. A current flows through the path ``, and the polarized relay J for detecting an incoming signal is activated, and the arrival of the incoming call is transmitted to the control circuit CONT via the contact j of the polarized relay J. Upon arrival of this incoming call, the control circuit CONT prepares a register to count the dial pulses subsequently sent from the opposing station, and when this register is ready, sends a dial tone or the like to the opposing station. After confirming this dial tone, the opponent station sends a dial pulse, but this dial information is also relayed by the polarized relay J, counted and stored in the register in the control circuit CONT, and this trunk is sent to the called extension telephone. Connected via a call path switch. Now, as soon as an extension phone is connected to this trunk,
As a response signal to the opposing station, relay E is operated to send a communication line polarity reversal signal to the opposing station, but since polarized relay J needs to continue operating even when relay E is operated, the contacts of relay E A continuous contact is used for e. Therefore, even during a call, the polarized relay J continues to operate, and will not recover unless the loop between the LA line and the LB line is closed as a recovery signal from the game party. Therefore, in the case of calling the local station first (restoring the destination) when receiving a call from the local station,
Only the relay E mentioned above is restored and only sends out a telephone line polarity reversal signal as a restoration signal to the opposing team.
Polarized relay J continues to operate. After confirming the restoration signal from the called side, the opposing team will open the loop between the LA and LB lines, and the polarized relay J will be restored for the first time, leaving this trunk empty.
It becomes available for the next outgoing and incoming calls. This is commonly referred to as a calling party release method used in trunk trunks to prevent collisions between outgoing calls and incoming calls. This means that the call ends when the calling party recovers, and even if the called party calls first (recovers first), the communication line between the two parties will not be recovered unless the calling party recovers. This method facilitates the exchange of outgoing and incoming trunks in both directions.

Next, when this trunk becomes the transmitting side, relays A, B, and BA are operated according to the transmission information from the control circuit CONT, so that "LA line - meter contact a of relay A - relay C
Break contact c - First winding of wire RPT0 - First winding of polarized relay D - Second winding of polarized relay D - Second winding of wire RPT0 - Make contact ba of relay BA Break contact c of relay C - make contact a of relay A - LB wire. ” loop consisting of the path
It is formed between the LA line and LB line and sends a start signal to the opposing team. However, since a current having a polarity opposite to the direction in which it operates flows through the polarized relay D, the polarized relay D does not operate. Next, when a dial tone or the like is sent from the opposing station as a dial pulse reception ready signal, the own station sends a dial pulse to the opposing station by turning contact a of relay A on and off. After sending the dial pulse, when the other station connects the called extension to this trunk, it sends out a line polarity inversion signal as a response signal. Here, when the opposite station sends a call line polarity reversal signal, a current with the same polarity as the direction in which it operates flows through the polarized relay D, so this polarized relay D operates and the call is possible. It is detected that the device is in a certain state. This polarized relay D is provided to detect the first call (previous recovery) of the game, and when it detects the recovery of the game, it sends information to the control circuit CONT via its contact d. In circuit CONT, a warning sound such as a tone is output to the calling extension telephone (on the local side) to notify that the game has been restored. As a result, if the calling extension telephone is restored, relays A, B, and BA are restored, and the other station and the own station are also restored.

In conventional trunk circuits, the calling side releases the loop between the LA line and the LB line as a recovery signal, then generally restores the trunk after a guard time of about 600 milliseconds or more, and then the called side makes the call. It is designed to be restored within about 300 milliseconds after opening the loop between the LA line and LB line from the side. For this purpose, the calling side must open the loop between the LA line and LB line of this trunk, and then
If the called party has not completed recovery after a guard time of about 600 milliseconds, the other party will continue to send the call line polarity reversal signal, causing a pseudo call to the calling party, and the system will be interrupted. This is by no means desirable in terms of control, and to prevent this, some trunk circuits are equipped with wire rings and polarized relays between the LA and LB lines, but adding these circuit components is not practical. Since this type of circuit is also disadvantageous, such circuits are rarely used in general loop-dial trunks.

The functions of the currently used loop-dial trunk circuits have been explained according to the circuit operation, but the polarized relays used for this are specially designed, expensive, and have small external dimensions. Therefore, the volume occupied by the circuit is also inevitably large, which is problematic. This has the disadvantage that it is particularly difficult to mount such a polarized relay on a printed circuit board, especially when attempting to miniaturize a device such as an electronic exchange. In addition, in order to reduce call loss in the trunk circuit,
In addition to the polarized relay, wire rings are also required, which poses problems in terms of cost, space, etc. As described above, in the conventional trunk circuit, it has been difficult to configure the circuit using inexpensive and small parts.

SUMMARY OF THE INVENTION An object of the present invention is to overcome these drawbacks and provide a trunk circuit for an automatic telephone exchange that is compact, economical, and stable in operation.

To achieve this object, the present invention connects a current direction detection circuit in parallel to an impedance connected in series with the direct current path of a trunk circuit of a telephone line connecting two automatic telephone exchanges, and detects the current direction. When a current in a preset direction to the circuit is on the DC current path, a predetermined signal is output to the output terminal of the current direction detection circuit, and that signal is used to send and receive signals between two automatic telephone exchanges. Furthermore, in order to more completely monitor the recovery operation of the trunk circuit, a comparator with high input impedance, that is, a potential difference polarity detection circuit, is connected between the two DC current paths of the trunk circuit. , until the trunk circuit is restored, that is, the trunk of the opposing station is completely restored, a predetermined signal is output to the output terminal of the potential difference polarity detection circuit, and that signal and the above-mentioned signal are used to connect the two automatic telephone exchanges. The system is configured to more reliably transmit and receive signals.

The present invention will be described in detail below with reference to the drawings.
FIG. 2 is a circuit diagram of the main part of the embodiment of the present invention. The present invention will be explained below in the same manner as in the explanation of FIG. In FIG. 2, when a loop is formed between the LA line and the LB line as an incoming signal from the opposing station, current flows through the two DC current paths of this trunk and the circuit that passes through the opposing station's loop. In other words, "Earth - Limiter circuit LMT ₁ - Resistor R7 - Relay
OG break contact og - Relay A1 break contact a ₁ - Diode D1 - LB line - Game loop -
LA line - Limiter circuit LMT0 - Zener diode
ZD0 - Transistor TR0 - Break contact a ₀ of relay A0 - Break contact og of relay OG - Resistor R
6-Battery. ” current flows through the inverter IC.
The output of 0 changes from low level to high level, and this output signal is transmitted to the control circuit CONT.
Note that the diode D1 is the transistor TR
This is to prevent excessive voltage from being applied between the emitter terminal and base terminal of transistor TR1, and to protect transistor TR1. It goes without saying that in this circuit, current also flows through the resistor R0 in parallel to the Zener diode ZD0 and the transistor TR0. Next, upon the arrival of this incoming signal, the calling side sends out a dial tone to the opposing station when it is ready to count and accumulate dial pulses from the opposing station.
The called extension is connected to this trunk by counting subsequent dial pulses. It goes without saying that the dial pulse at this time is received by the transistor TR0 and input from the inverter IC0 to the control circuit CONT. Next, when the called extension telephone answers, it sends out a telephone line polarity reversal signal by simultaneously operating relays A0 and A1 as a response signal to the other party, and the current flows between the two DC current paths of this trunk and the other party. The next route via the loop of
LMT1 - Resistor R7 - Break contact of relay OG og
- Relay A0 make contact a ₀ - Diode D0 - Limiter circuit LMT0 - LA line - Game loop - LB
Wire - Zener diode ZD1 - Transistor TR1
- Make contact a ₁ of relay A1 - Break contact og of relay OG - Resistor R6 - Battery. ” flows along the route. Note that the diode D ₀ is the transistor TR
Needless to say, it is there to protect 0.
As a result, transistor TR0 is restored and transistor TR1 operates, causing the inverter IC to
The output of 0 changes from high level to low level and
The output of the inverter IC1 changes from a low level to a high level, and from then on, this trunk becomes available for communication. It goes without saying that the relays A0, A1, and OG need not be poled relays and may be sufficiently compact relays.

Then the call ends and the called party picks up first (recovers first)
In this case, both relays A0 and A1 are restored, so a restoration signal is sent to the game player, transistor TR0 is activated, and transistor TR1 is restored. Next, when the loop between the LA line and LB line from the game side (sending side) is opened, transistor TR0 is restored, and logically, both transistors TR0 and TR1 are restored, so that game restoration is detected. This trunk can be restored.

Conversely, if the opposing station (calling side) makes the first call (recovers first), by restoring relays A0 and A1 of the own station, transistors TR0 and TR1
Both are in a restored state, and this trunk is in a restored state.

Also, if this trunk becomes the originating side, first the relay OG is connected from the control circuit CONT to the relay OG.
, then operate relay A0,
“The Earth of the Game – LB Line – Zena Diode ZD1 –
Transistor TR1 - Break contact of relay A1
a ₁ - Make contact of relay A0 a ₀ - Diode D0
- Limiter circuit LMT0 - LA line - Game battery. ”
A current flows through the path and sends a start signal to the game player. Next, when it becomes possible to count dial pulses from the opposing station, a signal such as a dial tone is sent out. On the other hand, for the game, the dial pulse is relayed to A0.
Sends out by contact a ₀ intermittent. When a call line polarity inversion signal arrives as a response signal for connection to the called extension telephone of the opponent station after sending a dial pulse, the "Line of the opponent station - LA line - limiter circuit LMT0" is sent.
-Zena diode ZD0 -Transistor TR0-
Make contact a ₀ of relay A0 - break contact a _{1 of} relay A1 - diode D1 - LB wire - game battery. ”
When current flows through the path of
TR0 operates, transistor TR1 is restored, and the output of inverter IC0 changes from low level to high level, and the output of inverter IC1 changes from high level to low level. These inverter ICs
0. Control circuit for changes in the output of IC1
By detecting CONT, it is possible to detect a response from the called party at the opposite station, and this trunk becomes available for communication.

Next, if the originating side recovers first, when the relay A0 is restored first, the loop between the LA line and the LB line is opened, and the originating side recovery signal is sent to the opposing station. In addition, after the relay A0 is restored, when the other party (the receiving side) sends out a communication line polarity inversion signal as a restoration signal, the resistors R8 and R9 with high resistance values
This can be detected by comparator IC2 via. Here, comparator IC2
diodes D6, D connected to the input terminals of
7 prevents excessive voltage from being applied to the input terminal of comparator IC2, and
This is to protect 2. Next, by detecting this call line polarity reversal signal, the relay OG
This prevents duplicate calls and enables stable operation of the circuit. Also, if the other party (called party) recovers first, the communication line polarity is reversed by transistor TR0.
is detected by the recovery of the relay A0 and the operation of transistor TR1, and sends a tone etc. to the calling extension telephone of the own office. When the calling extension telephone of the own office is restored, this trunk is put into the recovery state by restoring the relay A0. becomes.

In the case of transmitting and receiving signals, an embodiment of the present invention having the same function as a trunk circuit having a circuit for transmitting and receiving signals using a polarized relay and a wire ring for preventing call loss used in a crossbar exchange etc. As explained above, it is clear that this embodiment has the same function as a conventional trunk circuit equipped with a polarized relay, and furthermore, only three relays are used for one trunk circuit. Moreover, these relays do not have to be polarized relays, and can be sufficiently small.
In addition, although a relay for transmitting dial pulses is necessary for transmitting and receiving dial pulses, a relay for receiving dial pulses is not required, and the total number of times the relay operates is naturally reduced, which in turn lengthens the life of these relays. Needless to say, all other logic circuits can be integrated. As described above, the present invention has the advantage of providing a trunk circuit that is compact and economical and has a circuit that transmits and receives signals with stable operation.

Further, the above description does not limit the scope of the present invention, and it goes without saying that various modifications can be made to the present invention as necessary. For example, a current direction detection circuit having a series circuit of a Zener diode and a transistor can be replaced with other circuit elements such as a light emitting rectifier.
It goes without saying that various modified logic circuit configurations are also conceivable.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of the main part of a trunk circuit used in conventional crossbar exchanges, electronic exchanges, etc., and FIG. 2 is a circuit diagram of the main part of an embodiment of the present invention. CONT...Control circuit, CPU...Central control unit, LA, LB...Talking line, D, J...Polarized relay, A, B, BA, C, E, K, A0, A
1, OG...Relay, a, b, ba, c, d, e,
j, k, a ₀ , a ₁ , og...contact, RPT0~RPT
2, RPTA...wire, C0, C1, CA...capacitor, Rd, R0~R11...resistance, D0~D
7...Diode, ZD0, ZD1...Zena diode, TR0, TR1...Transistor, IC
0, IC1...Inverter, IC2...Comparator, LMT0, LMT1...Limiter circuit, 0...
Control circuit for the output signal of inverter IC0
Lead input to CONT, 1...Inverter IC
A lead that inputs the output signal of 1 to the control circuit CONT, 2...A lead that inputs the output signal of the comparator IC2 to the control circuit CONT.

Claims (1)

[Claims] 1. In a trunk circuit of an automatic telephone exchange that transmits and receives signals between the two automatic telephone exchanges by direct current flowing through a telephone line connecting the two automatic telephone exchanges, a first terminal and a second terminal is inserted and connected in series to the direct current path of the trunk circuit, and a first input terminal and a second input terminal are connected to the first terminal and second terminal of the impedance, respectively, for current direction detection. circuit, and when a current in the same direction as the direction from the first input terminal to the second input terminal of the current direction detection circuit exists on the DC current path, the current direction detection circuit detects the direction of the current. a first signal output means for outputting a predetermined signal to an output terminal of the trunk circuit, and a first input terminal and a second input terminal connected to a first DC current path and a second DC current path of the trunk circuit, respectively. The potential difference polarity detecting circuit and the potential difference having the same polarity as the direction from the first input terminal to the second input terminal of the potential difference polarity detecting circuit connect the first DC current path and the second DC current. a second signal output means for detecting the polarity of the potential difference when it exists between the paths and outputting a predetermined signal to the output terminal of the potential difference polarity detection circuit, the first signal output means and the second signal output means; A trunk circuit of an automatic telephone exchange, characterized in that a recovery operation of the trunk circuit is monitored by a signal output means.