JPS6337547B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polarity reversal detection circuit for a central office line for detecting a called party's response and preventing incoming call collision in an automatic reporting device or the like connected to a telephone circuit.

In order to avoid notifying an incoming call when an automatic notification device attached to a telephone makes an automatic notification, it is necessary to send a selection signal after confirming that no incoming signal has arrived at the telephone. Yes (this is called incoming collision prevention). Further, the notification needs to be sent after the selection signal is sent and after the called party answers.

By the way, in the current telephone switching network, when communication is carried out between telephone terminals, as shown in Figure 1, there are states A to E between the calling side and the called side, and the polarity of the central office line L1 and L2 terminals indicates the start of mutual communication. Invert several times. In other words, the transmitting side picks up the handset (off-hook),
When the dial is operated (selection signal sent) and the called party goes off-hook (response), and when the called party receives a calling signal and goes off-hook.

When the above-mentioned ringing signal arrives, the polarity reversal occurs independently of the 16 Hz bell ringing signal, so the polarity reversal occurs at the same time as or in advance of the 16 Hz bell ringing signal. Therefore, when automatically reporting, if 16Hz
Even if there is a pause time in the bell ringing signal, collision of incoming calls can be prevented by detecting the polarity reversal described above and controlling the device using the detection signal. On the other hand, if the incoming signal has not arrived, after acquiring the central office line, a selection signal is sent to call the called party, and if the polarity reversal of the central office line is detected when the called party answers, the detection signal is sent. It is possible to control the device and perform a predetermined reporting operation.

A conventional example for detecting such a polarity reversal operation is shown in FIG. 2, which is a station line circuit diagram of an automatic notification device. Changeover switches TK1 to TK4 between the office line circuit 1 and the telephone set 2 of the automatic notification device are switched to the automatic notification device side and connected, and one end of the start-up make switch st of the device is connected to one of the office lines L1 and L2. At the other end, there is an incoming collision prevention circuit 3 in which the light emitting diode of the photocoupler PC1 and a high resistance R1 are connected in series and connected to the other side of the central office line. Connect them in parallel with opposite polarities,
It was equipped with a called party response detection circuit 4 connected in series to the central office line.

However, in this conventional called party response detection circuit 4, since a light emitting diode of a photocoupler is provided in series with the office line, a DC voltage drop occurs on the office line due to the issuing diode, and the equivalent series resistance of the device increases. In some cases, it was necessary to limit the length of subscriber lines.

Furthermore, since the incoming call collision prevention circuit 3 and the called party response detection circuit 4 are provided independently, the number of components increases.
It wasn't economical.

The present invention has been made in view of these conventional drawbacks.

Next, the present invention will be explained in detail based on the drawings.

FIG. 3 is a station line circuit diagram of an automatic notification device showing an embodiment of the present invention, in which 5 is a calling signal detection circuit DET for detecting a 16Hz calling signal, 6 is a polarity reversal detection circuit, and 7 is a selection signal. Sending circuit, 8 is a message sending circuit, st is a start make switch, which is the contact point of the start relay ST which is not shown in the drawing, h1, h2 is a hold make switch for capturing the station line, which is a hold relay which is not shown in the drawing. Contact point of H, R1, R2 is R1>R
Among the resistors having a relationship of 2, R1 has particularly high resistance.

PC4 and PC5 are photocouplers, and the collector and emitter of each transistor are connected to the control section of the automatic notification device. The same symbols as in FIG. 2 indicate equivalent parts.

FIG. 4 is a block diagram of the control section of the automatic notification device, which is controlled by the output signals of the photocouplers PC4 and PC5 of the polarity reversal detection circuit 6, which detect polarity reversal. Reference numeral 9 indicates the input of the start signal of the device, 10 is the input signal monitoring circuit, 11 is the control circuit, 12 is the dial number storage section, 13 is the relay drive circuit, 131 is the holding relay H, and 132 is the start relay ST. , the same symbols as in FIG. 3 indicate equivalent parts.

FIG. 5 is a time chart showing the polarity reversal detection state of the automatic notification device. The same reference numerals as in FIG. 4 indicate equivalent parts.

Further, the arrows indicate the sequence of operations regarding each signal.

Next, the operation will be explained.

When an activation signal (fire, theft, or other input signal) is input to this device, the signal is input to the control circuit 11 via the input signal monitoring circuit 10. At this time, if a call is already incoming, the 16Hz ringing signal detection circuit 5
Because there is a signal from
If there is no incoming call, the control circuit 11 switches to the relay drive circuit 1.
Drives the ST relay through 3 and closes the st contact L1
-TK1-st-R1-PC4-TK2-L2 loop for a certain period of time (16Hz ringing signal rings for 1 second
Since it is an intermittent signal with pauses of seconds, monitor the polarity of the station line (at least 2 seconds, which is the same as the pause time of the 16Hz signal).

Now, if the L1 side of the office line is positive and the L2 side is negative, current flows to the light emitting diode side of the photocoupler PC4, and if a call is received within the certain period of time, the polarity of the office line is reversed, and the current photocoupler PC5 emits light. flows to the diode. The change in polarity at this time is detected by reversing the potentials of the output transistors a and b of the photocouplers PC4 and PC5 shown in FIG. It is determined that the has arrived,
without performing a reporting operation, via the relay drive circuit 13.
Restore ST relay 132 and open the st contact. This operation is shown in the time chart of FIG. 5A.

On the other hand, if the incoming signal does not arrive within the certain period of time, there is no change in the potentials of the outputs a and b of the transistors, and the signal from the control circuit 11 is sent via the relay drive circuit 13 to restore the ST relay to the ST relay. The contact is opened, the H relay is operated, the h1 and h2 contacts are closed to capture the central office line, and the selection signal sending circuit 7 is driven to send out the subscriber number already stored in the dial number storage section. After sending the selection signal, the control circuit 11 again drives the ST relay via the ST relay drive circuit 13 to close the ST contact and prepare for the arrival of the called party response detection signal.

When the called party is called and the called party answers, the polarity of the office line is reversed, the L2 side becomes positive and the L1 side becomes negative, and the output a of each of the photo couplers PC4 and PC5 is similar to the change in polarity when receiving a call described above. ,b
The polarity of is reversed. Here, R1 is selected to have a high resistance so that the current flowing through the loop formed when an incoming call is detected will not be considered as a central office line capture by the exchange side, and R2 is a high resistance value that will prevent the exchange side from regarding the current flowing through the loop formed when an incoming call is detected as central office line acquisition.
Since the DC voltage between 1 and L2 drops, R1>R2
This ensures low resistance and stable operation of the photocoupler. The photocoupler PC4, PC5
When the called party response is detected by inverting the potentials of the outputs a and b, the control circuit 11 restores the ST relay via the relay drive circuit 13 and opens the ST contact.
The polarity reversal detection circuit 6 is disconnected, the message sending circuit 8 is driven, and a predetermined message is sent. This operation is shown in the time chart of FIG. 5B.

In addition, in the explanation, the normal polarity of the station line is positive on the L1 side,
Although the L2 side was set as negative, the normal polarity of the station line is L1.
The effect is the same even if the L2 side is negative and the L2 side is positive.

Further, in the embodiment, the starting make switch and the holding make switch are both relays as metal switches, but it is clear that they can be replaced with electronic switches. Furthermore, when sending a message, the polarity reversal detection circuit is disconnected in this explanation, but if R2 is connected even while sending a message, the polarity reversal caused by the callee can be detected in advance and the notification can be stopped immediately. becomes possible.

As explained above, according to the present invention, since the polarity reversal detection circuit is connected in parallel to the telephone set, the DC voltage drop in the communication circuit is small, and the incoming call collision prevention circuit and the called party response detection circuit are connected in parallel. Because the circuits are shared, the circuit becomes simple and can be constructed using fewer parts, so its practical effects are extremely large.

[Brief explanation of the drawing]

FIG. 1 is an operation diagram showing polarity reversal of a telephone line, FIG. 2 is a central office line circuit of an automatic notification device showing a conventional central office line reversal detection circuit, and FIG. 3 is an automatic notification device showing an embodiment of the present invention. FIG. 4 is a block diagram showing the control unit of the automatic reporting device, FIG. 5 is a time chart showing the polarity reversal detection state, 1... Office line circuit of the automatic reporting device, 2... Telephone, 3
... Incoming call collision prevention circuit, 4... Called party response detection circuit,
5... 16Hz calling signal detection circuit, 6... Polarity reversal detection circuit, 7... Selection signal sending circuit, 8... Message sending circuit, 9... Starting signal, 10... Input signal monitoring circuit,
11... Control circuit, 12... Dial number storage section, 1
3... Relay drive circuit, 131... Holding relay, 132...
Starting relay, PC1 to PC5...photo coupler, L1,
L2...Station line, TK1~TK4...Switch switch.

Claims (1)

[Claims] 1. In a device that is connected to a central office line and has the function of preventing incoming call collision and detecting a called party response, a circuit in which the polarities of the light emitting diodes of two photocouplers are connected in parallel with each other in opposite directions, and a circuit for activating the device. one end of a series circuit formed by connecting a make switch and a resistor R1 in series to one of the office wires,
A holding make switch for connecting the other end to the other side of the office line and capturing the office line; and R1>
A polarity reversal detection circuit characterized in that a circuit in which a resistor R2 connected in series is provided in parallel with the resistor R1.