JPH02270448A - Constant current feeder to terminal equipment of telephone circuit provided with line selection adaptor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention is applicable to telephone exchange lines, telephone equipment, etc. in order to select any telephone line from among the telephone lines installed by NTT and other type 1 telecommunications carriers. The present invention contributes to eliminating the disturbance that is a source of noise on the telephone set due to the inflow of noise current into the office line side caused by the operation of the line selection adapter attached between the telephone terminal and the telephone terminal. By adding and installing the constant current power supply device in the line selection adapter, it is possible to exhibit a portable failure elimination effect for any type of telephone.

``Prior Art'' FIG. 2 shows a terminal T1 to which a telephone office line (L) and a terminal device such as a telephone are connected. This is a conventional circuit configuration diagram with a terminal (T) equipped with T2 and a line selection adapter with built-in functions described below.The digital unit has a CPU, ROM,
, MODEM dual tone φ multi-frequency transmitting/receiving IC is built-in.

Therefore, if there is a type 1 carrier such as A, BSC, etc., the husband's access code will be added to the front of the other party's normal long-distance number, local number, or telephone number, and this will be sent by dialing. Then, the exchange switches to the line of one of the above carriers. The above data recorded in the adapter memory via the modem built into the adapter's CPU can be rewritten using a telephone line.

A 0N10FF hook relay 3.0N10FF hook detector 4, a polarity/ringer detector 7, a dial pulse sender 5, and a hike P'' lid circuit 6 are connected to the office line, and when the office line arrives, the polarity/ringer detector 7 is detected and terminal 4
The 0N10FF hook relay, which connects to the terminal when OFF-hook, is regarded as an OFF-hook response and maintains a direct connection between the terminal and the central office line, but if it is dropped during an incoming call, the 0N10FF hook relay connects to the terminal.
The call is assumed to be an F-hook call and the following operations are performed. That is, after detecting the terminal's OFF hook and dial tone, switching the direct connection between the office line and the terminal to the adapter side, detecting the dial tone again, receiving the dial, and determining the lowest rate line,
After completion of dialing, a series of operations are performed to return the station line and terminal that have been switched to the adapter side to a direct connection state. In the above-mentioned dial reception, if the number is a local number, it is dialed as is by the dial pulse, and if it is a long-distance number, the above-mentioned access code added to the beginning is added based on the judgment as to whether it is the lowest charge line and the number is dialed out. Here, the dial pulse detector 13 sends a dial pulse signal from the terminal to the constant current power supply unit 2, and if necessary, adds an access code +l to the beginning and sends it to the dial pulse sender 5 and the station 8. Sent out.

When the terminal side is switched from the office line side to the adapter side, the transistors Q, Q4 of the constant current feeding section are controlled by a polarity switching signal SPc from the CPU so that the polarities of the office line and the terminal are aligned.

By the way, the problem to be solved by the present invention is that when the terminal is switched from the central line to the adapter side, the constant current power supply section supplies direct current to the terminal as well as the adapter, but the terminals T, T2 and the adapter are , because it is grounded through a semiconductor element such as a diode, the CP is connected to the telephone connected to the terminal.
In some models with a built-in U, noise current flows from the AC line that energizes the CPU to the office line via the adapter, so even if you switch the AC side polarity of the phone, you can still hear the noise. This is what is happening.

The cause of this failure is due to the connection between the adapter and the terminal via ground.

``Problem to be solved by the invention'' However, as mentioned above, in order to prevent the ground current from flowing into the adapter from the telephone side, the constant current power supply section is kept electrically floating from the ground. 0 ``Means for solving the problem'' First, in order to electrically isolate the adapter and the power supply, a DC/DC converter is used to electrically isolate the primary and secondary AC In addition to electrically isolating the next side using a transformer, when the switching element in the constant current power supply section is not conducting, the control side is maintained in a high impedance state with the conducting section by means such as a photocoupler to measure electrical isolation. This is what I did.

An embodiment of the present invention will be explained in detail below with reference to FIG.

Embodiment In FIG. 1, parts equivalent to those in FIG. 2 are represented by the same symbols, and a part of the adapter is omitted. 100 is a transformer TJIII which receives the DC input voltage E.

By opening and closing the secondary side of the converter, it is converted to any secondary output voltage and taken out, and multiple DC outputs EDC, , EDC2ED
A DC/DC converter that obtains C is used as the power source for the constant current power supply section, and PCl and PC2 are the switching elements Q, Q4, and Q2 in the bridge configuration of the constant current power supply section 2.
A photoelectric coupler that applies a control signal to the husband's control pole for the pair of and Q, 13o is a dial pulse detection coupled with a photoelectric coupler PC1! , RFC is a rectifier that protects each of the above-mentioned switching elements, ・DC voltage is applied to the AC side terminals A and H from the constant current feeder, and the DC voltage is applied to the DC side terminal C%D. The stabilized DC output voltage of the C/DC converter (Jpc3 is added. SPC uses the terminal T as the same as the office line dial pulse signal SDP (the above CPU
It is sent to the exchange via V. SA is a dial progress tone signal and is sent from the exchange as an analog signal, and both ends of the secondary winding of the transformer T2 are connected to the AC side terminals A and B of the rectifier.

With the above configuration, the constant current power feeding section built into the line selection adapter is maintained in an electrically insulated state between the central office line that connects to the exchange and the terminal that connects to the telephone by the transformer and optical power grapher. The ground current flow path is completely cut off.

``Effect J: Thus, when a line selection adapter is installed near a telephone, regardless of the model of the telephone, the constant current power supply section exerts an isolation function within the adapter, cutting off the path of noise current. When the terminal side is switched from the central office line side to the adapter side, the polarity can be changed to be the same, so there is no need to switch the AC side polarity of the telephone, and it is portable and can be used to prevent problems such as noise generation. This contributes to achieving the desired effect.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of a constant current power supply device built into a line selection adapter of the present invention, and FIG. 2 is a conventional circuit configuration diagram. T: Terminal, L: Office line, 100: DC/DCC/formula-
Ta, Q, ,Q2. Q, ,Q4 switching element,
PC,, PC2, PC,: Photoelectric coupler, 130: Dial pulse detector, 2: Constant current power supply section, Tl, "2"
Transformer, 12: Digital unit.

Claims (1)

[Scope of Claims] [Registered Trademark] An adapter for arbitrarily selecting at least one telephone line from a plurality of telephone lines of a plurality of Type 1 telecommunications carriers, etc. including NTT, between a central office line and a terminal such as a telephone set. In a telephone line power supply device that is attached between the terminal and supplies a constant current to the above-mentioned terminal, a DC power source that converts one DC source into a plurality of different DC outputs as an input.
/DC converter, and applying the DC constant voltage using the DC/DC converter as a DC source to the AC side terminal of the rectifier, and connecting at least one positive and negative output terminal of the DC/DC converter between the DC side terminals. A bridge circuit with switching elements in four arms is connected, and each pair is equipped with a photoelectric coupler that connects two pairs of different polarities of the switching elements with a common polarity switching signal in response to the operation of the adapter. A constant current power supply device to a terminal of a telephone line equipped with a line selection adapter, characterized in that a constant current power supply having an isolator device included in the line selection adapter is coupled to the terminal side. .