JPH0418283Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a pole reversal signal detection circuit for a public telephone.

[Conventional technology]

In public telephones, charges are made when coins are collected, depending on the caller's response and the passage of unit call time.For the purpose of instructing this charge,
A polarity reversal signal is sent from the exchange, and the public telephone side detects the arrival of the polarity reversal signal and charges accordingly.

However, the polarity reversal signal is the line terminal of the public telephone.
In addition to defining L ₁ as the positive pole and the same terminal L ₂ as the negative pole,
This polarity is reversed and comes from the telephone line, so if you connect the telephone line to the line terminal with the wrong polarity when installing a public telephone, it will be impossible to detect the polarity reversal signal and you will not be charged. produce defects.

As a countermeasure against this, a configuration disclosed in Japanese Utility Model Publication No. 58-40679 has been proposed, in which the initial polarity of the loop current that flows when the DC loop of the public telephone is closed is memorized, and the loop current is passed in the opposite direction to the memorized loop current. The polarity of the current is monitored and a polarity reversal signal is detected based on this.

[Problem that the invention attempts to solve]

However, the configuration according to Japanese Utility Model Publication No. 58-40679 uses a flip-flop circuit to store the initial polarity, and also requires a polarity determination pulse generation circuit to set the storage operation time point, resulting in an overall complicated configuration. In addition to being expensive, this method poses problems such as being unable to detect disconnections in telephone lines, failures in the loop current polarity detection circuit, and the like.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention is constructed by the following means.

That is, a public service system that stores the initial polarity of the loop current that flows when the DC loop is closed, monitors the polarity of the loop current that runs in the opposite direction to the loop current of the memorized initial polarity, and detects a polarity reversal signal that comes from the telephone line. In a telephone, a diode bridge is inserted into a DC loop with the input side as the telephone line side, and a first circuit detects a loop current in a fixed direction passing between the telephone line and the input side of the diode bridge.
a second loop current detection means for detecting a bidirectional loop current passing through the diode bridge on the output side of the diode bridge; and determining means for determining the arrival of a polarity reversal signal based on each detection output.

[Effect]

Therefore, the first loop current detection means can obtain a detection output according to the polarity of the line terminal,
The second loop current detection means can obtain a detection output that is independent of the polarity of the line terminal, and depending on the combination of these detection output conditions, it is possible to not only determine the arrival of a polarity reversal signal, but also detect telephone line disconnection and failure. It is also possible to detect the following.

〔Example〕

Hereinafter, details of the present invention will be explained with reference to figures showing embodiments.

FIG. 1 is a configuration diagram showing the main parts, and for the line terminals L ₁ and L ₂ to which the telephone line is connected, there is a switch HS ¹ and a one-way detection circuit (hereinafter referred to as SDT) 1, diode
Diode bridge (hereinafter referred to as DB) with D ₁ to _{D 4}
2. Close the DC loop via a bidirectional detection circuit (hereinafter referred to as BDT) 3 as a second loop current detection means and a disconnection circuit (hereinafter referred to as CB) 4 using a switching element such as a transistor. A telephone circuit (hereinafter referred to as TKC) 5 is connected,
When the DC loop is closed by turning on the switch HS ¹ in response to the off-hook, a loop current with the line terminal L ₁ as the positive terminal is passed by the power supply of the exchange via the telephone line, and the dial key and dial circuit in TKC5 make a dial call. In response to this, the exchange makes an exchange connection, and if the other party responds, the exchange sends out a polarity reversal signal with line terminal _L2 as the positive pole, so SDT1 and
Based on the signals as each detection output of BDT3, a processor such as a microprocessor (hereinafter referred to as
A control circuit (hereinafter referred to as
CNT) 6 determines the arrival of a polarity change signal, controls a coin processing unit (hereinafter referred to as CPS) 7, and stores coins that have been inserted and are waiting, and
TKC5 allows you to freely talk to the other party.

As the call continues, a polarity change signal also arrives every time the unit call time determined by the distance from the ground to the other party elapses, so that billing is also done by storing coins.

In other words, SDT1 and BDT3 are each photocoupler (hereinafter referred to as PC) inserted into the DC loop.
Light emitting diodes (hereinafter referred to as LEDs) 8 and 9, resistors R ₁ and R ₈ for current limiting, and varistors VR ₁ and VR ₂ connected in parallel with these for bypassing current in the opposite direction and for preventing overvoltage application. , PC8, 9 photodetector transistors (hereinafter referred to as PTR), and resistors R _{2 and} R ₄ that apply power V to the collectors of these transistors. With the loop current,
In contrast, PC8 inserted in the forward direction
The LED emits light and turns on the opposite PTR to change its collector potential from "H" (high level) to "L".
(low level), and this signal is sent as a detection output by loop current in a certain direction, and CNT6
In contrast, when a polarity reversal signal arrives, the PC
The signal does not go through to LED 8, which goes out and turns off the PRT, so the signal becomes "H" at this time.
Given to CNT6.

In addition, BDT3 is inserted into the output side of DB2 whose input side is on the line terminals L ₁ and L ₂ , so that the loop current always flows in the same direction regardless of the polarity of the line terminals L ₁ and L ₂ . , In response to this, the LED of PC9 inserted as a forward direction emits light, turns on the opposing PTR, sends out an "L" signal, and in order to give it to CNT6, it is connected between line terminals L ₁ , L ₂ and DB2. The loop current that flows is a detected bidirectional loop current.

Figure 2 is a flowchart of the judgment status performed by the CNT6 CPU.The CPU executes instructions in memory and accesses the necessary data from the memory. ² 's output says "Off hook?"
Check 101 and depending on the Y (YES) of this
Execute "signal A, B check" 102 from SDT1 and BDT3, and check "A=?・B=?"10
3 to find these situation combinations and write “A=
If it is "L・B=L" 111, it is the initial state with the line terminal L ₁ as the positive electrode, and if "A=H・B=L" 112, it is the initial state with the line terminal L ₂ as the positive electrode. Since the initial polarity is also normal, this initial polarity is stored in the "initial state/memory storage" 113.

On the other hand, if "A=L・B=H" 121, the BDT3 signal is abnormal, it is determined that the BDT3 has failed, and the "failure processing" 122 is performed to control CB4 to open the loop, etc. Public telephones shall be rendered unusable by means of:

Also, if "A=H・B=H" is 131, it means that the telephone line has been disconnected or there is a malfunction inside the telephone.
"Line disconnection/failure/processing" 132 makes the line unusable as in step 122.

On the other hand, following step 113, after the coin is inserted and the dial is dialed, the switch is turned on.
Check "On hook?" 141 by the output of HS ² , and if this is N (NO), proceed to step 1.
As in 02, "signal A, B check" 142 is performed, but in response to Y in step 141, it is determined that the call is on-hook due to the end of the call, and "call end processing" 143 is performed to return the coin and control CB4. Open the loop, etc.

Further, N in step 141 is the start or continuation of a call, and step 142 is followed by "A=L・B=H?" 151, similar to step 103.
“A=H・B=H?” 152 and “A, B=Initial state?” 153 are sequentially determined, and step 151 is Y.
If , it is a failure like in step 121, and the process moves to step 143, but if Y in step 152
In this case, since there is also a momentary interruption of the loop on the switching connection, steps 141 and subsequent steps are repeated, and in response to Y in step 153, it is determined that the polarity reversal signal has not yet arrived.
Similarly, while repeating steps 141 onwards,
If step 153 becomes N and the initial polarity and the signal do not match, it is determined that a polarity reversal signal has arrived, and CPS7
161, and in response to the storage confirmation signal from the CPS 7, checks the ``coin storage?'' 162, and if this is Y, repeats steps 141 onwards, while repeating step 16.
According to N in 2, "forced disconnection processing" 1 opens the loop and restores the exchange under the control of CB4.
Do 63.

Therefore, regardless of whether the positive terminal of the telephone line is connected to line terminal L ₁ or L ₂ , the polarity reversal signal can be detected accurately, making it possible to perform billing reliably and to Failures including line disconnection can also be reliably detected.

Note that if it is particularly necessary to detect disconnection of the telephone line, predetermined processing may be performed in response to Y in step 152.

3 to 5 are main circuit diagrams showing other embodiments, and in FIG. 3, SDT1 and
A relay is used as BDT3, and relay RL ₁ ,
RL ₂ is inserted into the input side and output side of DB2, and a diode D ₁₀ is connected in parallel to relay RL ₂ , so that it responds only to loop current in a certain direction, and these contacts RL A power supply V is applied through resistors R ₂ and _{R 4} in series with R 1 and rl ₂ , and a signal is obtained in the same manner as in FIG.

Figure 4 shows the case where transistors (hereinafter referred to as TR) are used, and are connected to the input side and negative output side of TR, Q ₁ , Q ₂ , and DB2, respectively, so that they turn on when they have negative polarity. Diode D ₁₁ ,
D ₁₂ , resistors R ₁₁ , R ₁₄ , TR・Q ₁ , Q ₂ that provide bias to the bases of TR・Q ₁ , Q ₂ through these
A resistor R ₁₂ connected between the base and emitter of
_{SDT1 and ​ ​ ​}
BDT 3 is configured, and when the polarity of the point where the cathodes of diodes D ₁₁ and D ₁₂ are connected is negative, TR・Q ₁ and Q ₂ are turned on, and the power supply V _D is connected to the resistors R ₁₃ and R ₁₆ , and the signal is sent out as "H".

Fig. 5 shows the case where SDT1 similar to Fig. 1 is inserted in series with diode _D1 of BD2, and here too, since a loop current in a certain direction flows only when line terminal _L1 is positive, Results equivalent to those in FIG. 1 are obtained.

Note that the SDT1 may be inserted at the input side of the diode _D1 , and the same result can be obtained by inserting it in series with the diodes _D2 to _D4 , so the line terminals _L1 , _L2 and DB2 The SDT 1 shown in FIGS. 3 to 5 can be inserted into any position between the output + and - sides.

In addition, the configuration of SDT1 and BDT3 can be selected arbitrarily depending on the situation, and as CNT6
Equivalent functions may be realized by various logic circuits without using a CPU and memory, and the configuration shown in FIG. 1 may be selected according to conditions such as charging by a fee card.

Furthermore, in Figure 2, various modifications can be made, such as replacing each step with another equivalent step, changing the order, or omitting unnecessary steps, depending on the situation. .

[Effect of idea]

As is clear from the above explanation, according to the present invention, with a simple and inexpensive configuration, polarity reversal signals can be detected accurately and billing can be performed reliably, regardless of the connection polarity of the telephone line to the line terminal. In addition to being able to detect failures, this system provides great benefits for various public telephones.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, Fig. 1 is a configuration diagram showing the main parts, Fig. 2 is a flowchart of the judgment situation,
3 to 5 are main circuit diagrams showing other embodiments. 1...SDT (unidirectional detection circuit), 2...DB (diode bridge), 3...BDT (bidirectional detection circuit), 5...TKC (talking circuit), 6...CNT (control circuit), 7...CPS (coin processing unit), L ₁ , L ₂
...Line terminal, HS ¹ , HS ² ...Hook switch.

Claims (1)

[Scope of utility model registration request] storing the initial polarity of the loop current that flows when the DC loop is closed, and monitoring the polarity of the loop current that runs in the opposite direction to the loop current of the stored initial polarity;
In a public telephone that detects a polarity change signal coming from a telephone line, a diode bridge inserted into the DC loop with the input side as the telephone line side, and between the telephone line and the input side of the diode bridge. a first loop current detection means for detecting a loop current flowing in a certain direction; and a second loop current detection means for detecting a bidirectional loop current flowing through the diode bridge on the output side of the diode bridge. , and determining means for determining the arrival of the polarity reversal signal based on the respective detection outputs of the first and second loop current detection means.