JPS6364456A - Side tone preventing circuit for key telephone set - Google Patents

Abstract

PURPOSE:To surely prevent side tone by deciding an optimum balancing circuit of a 2-4 wire conversion circuit corresponding to each trunk line dial number at the installation of telephone sets and selecting the optimum balancing circuit depending on dial information in receiving a trunk line dial number. CONSTITUTION:Several kinds of balancing circuits 13 are provided to the 2-4 conversion circuit 11 and they are connected to the circuit 11 via a switch 12 respectively. Since the line impedance changes with different installation location and talking party, talking is made to each trunk line actually from the installed location to decide an optimum balancing circuit among the balancing circuit prepared for each trunk line and the result is stored in a storage section 15. A control section 14 obtains a data to change over a switch to select an optimum balancing circuit from the storage section 15 based on dial information for a called party in case of dialing and used the data to select a corresponding switch thereby selecting the optimum balancing circuit 13, by which side tone is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a 2-4 wire conversion circuit for a button telephone, and in particular, to automatically change the balanced circuit of the 2-4 wire conversion circuit to an optimal circuit when making a call. The present invention relates to a side sound prevention circuit in a 2-4 line conversion circuit of a button telephone.

[Conventional technology]

FIG. 2 shows the configuration of a 2-4 wire conversion circuit of a conventional key telephone. In the figure, %18 is the central office line, 17 is the received signal,
19 is a transmission signal.

As is clear from FIG. 2, one balance circuit 21 is connected to the 2-4 wire conversion circuit 11 and is fixed.

(Problem to be solved by the invention) Therefore, in the conventional 2-4 wire conversion circuit of a key telephone, if the line impedance changes depending on conditions such as the installation location and the destination, the balance of the 2-4 wire conversion circuit will be affected. Collapse,
It has the disadvantage of increasing sidetone.

The purpose of the present invention is to solve the above-mentioned drawbacks, and in view of the fact that line impedance varies depending on the installation location and the destination of the call, by selecting the most suitable balanced circuit at the time of making a call, it is possible to reliably respond to changes in line impedance. An object of the present invention is to provide a side sound prevention circuit for a button telephone that can completely prevent side sound.

(Means for Solving the Problems) In order to achieve the above object, the sidetone prevention circuit for a button telephone according to the present invention includes at least one balanced circuit and a 2-4 wire conversion circuit for each balanced circuit. A switch for connecting to the telephone, a memory section that stores the data, and a memory section that stores and processes dial information. and a control circuit that reads out the corresponding data from the storage section when receiving the central office line calling number by the controller, and performs control to turn on the optimum balance circuit and the connector switch.

(Actual flow side) Next, one aspect of the present invention will be explained with reference to all the drawings.

FIG. 1 is a block diagram showing one embodiment of a side sound prevention circuit according to the present invention.

Several types of balance circuits 13 are provided for the 2-4 wire conversion circuit 11, and each is connected to the 2-4 wire conversion circuit via a switch 12. By changing the switch 12, the side sound can be minimized.

The switch 12 is controlled by a controller 14.

Data for selecting the optimal balance circuit 13 is obtained by a method of training in advance.

In other words, the impedance of the line changes depending on the installation location and the destination of the call, so when installing the telephone, actually make a call to each office line from the installation location, and select the optimal balanced circuit from among the balanced circuits prepared for each office line. Determine the balanced circuit,
The data is stored in the storage unit 15.

When making a call, the control section 14 obtains data for switching to the switch in order to select the optimum balanced circuit for the storage section 15 according to the dial information of the called party, and performs 2-4 wire conversion by switching to the corresponding switch based on this data. Times! fs1
The optimum balance circuit 13 is selected to reduce sidetone.

(Effects of the Invention) As explained above in detail, the present invention provides a button filling machine with two
- Various types of balanced circuits are prepared in the 4-wire conversion circuit, and it is configured to select all the optimal balanced circuits from pre-trained data depending on the dial number when making a call, so it can cope with different states of line impedance. It has the effect of completely reducing side sounds.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the side sound prevention circuit in the 2-4 wire conversion circuit of the button 1L pasted iso according to the present invention;
The figure shows the configuration of a conventional 2-4 line conversion circuit. 11... 2-4 wire conversion circuit 12... Selector switch 13... Balance circuit 14.
...Switch control section 15...Storage section 16...Dial information 17...Call reception 11! No. 18... Bureau +!
l 19...Transmission Iba No. 2J...Balanced circuit

Claims (1)

[Claims] In button telephones, there is at least one balanced circuit, a switch for connecting each balanced circuit to a 2-4 wire conversion circuit, and when the telephone is installed, it is ideal for making calls from the installation location and corresponding to each central office line calling number. Determine the optimal balanced circuit, and when the central office line dialing number is received from the dial information, read the corresponding data from the storage section, and connect the optimal balanced circuit. A side sound protection circuit for a button telephone, consisting of a control circuit that controls turning on the switch.