JPS61263398A - Key telephone system - Google Patents

Abstract

PURPOSE:To relieve the line distance limitation in relation to the main equipment by correcting the line impedance of a key telephone system during a speaking between extensions to a specified value, and by making it conform to the impedance of a line of distance corresponding to the balancing circuit. CONSTITUTION:The distances of lines L1-Ln of the key telephone systems T1-Tn installed at optional places are calculated by terminal voltage detectors 6 and 9, and the resulting values are stored in a memory part 3. In case the telephone set T1 and that T2 are used for speaking utilizing a microphone 17 and a speaker 19, the controller 2 reads out the distances of the lines L1 and L2 from the memory part, and adds them together, and controls a switch controller part 14 to select an impedance from impedance correcting circuits 11-13 that conforms to the balancing circuit 15. In such way, a tone is unified for any optional length of line and a howling is prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a button telephone device, and more particularly to a device that performs internal calls using the microphone and speaker of the button telephone.

[Conventional technology]

Key telephone devices have been widely installed in offices, stores, etc. because they allow multiple telephones to share multiple office lines, transfer calls, and make inter-extension calls. Since button telephones can be easily installed anywhere, the installation distance between telephones varies depending on various situations, such as in a slightly remote location of a large office or in a residence that is also used as a store. However, the distance between key telephones when making an extension call varies greatly depending on the installation situation and the combination of telephones used when making an extension call.

Now, this type of button telephone device is generally a button telephone,
The key telephone is comprised of a main unit and a communication path that connects it, and the key telephone is equipped with a handset, a 2-wire 4-wire conversion circuit, and a balancing network, which are used for calls using a microphone and speaker. This compensates for the effects of distance between key telephones, but normally this network is only suitable for a certain distance, so for example at a distance of approximately A, which is the maximum extension distance specified for the button telephone equipment. [Problems to be Solved by the Invention] Conventional button telephone devices have been designed to accommodate various installation conditions of button telephones through a balancing network;
The designed balancing network thus only fits at a certain point in the extension distance between the main device and the key telephone, and thus any difference in this distance will result in howling, thus limiting the maximum extension distance and the microphone/speaker distance. Volume restrictions are imposed, which may cause practical problems, and the length of the communication path is shorter when making an internal call compared to an external call, so [Means for Solving the Problem] The present invention provides a key telephone that compensates for calls using a microphone and a speaker using a balancing network. The main device, which is equipped with a balancing network adapted to the extension distance, and which is connected to each button telephone via a communication path, detects the terminal voltage due to the constant communication current at the main device end of the communication path, and connects each button telephone to the main device. A means for calculating and storing the distance between the telephones and the device, and a means for reading out the stored distance at the time of any internal mutual communication using the microphone and speaker, and calculating the impedance between each button telephone set connected in series via the main device. ``means for correcting and adapting the impedance of the distance corresponding to the predetermined balancing network.

[Effect]

The line impedance can be isometrically approximated to the impedance of the longest internal line distance specified by the button telephone device.

〔Example〕

First, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a button telephone device showing one embodiment of the present invention. 1 is a main device, Tl to Tn are key telephones, L1 to Ln are communication paths, and main device 1 is connected to key telephones T1 to Tn by communication paths L1 to LH, respectively. The main device 1 includes a control section 2 that controls each section;
A storage unit 3 that stores the distance between the main device 1 and each button telephone TI-'rn, and a constant current supply circuit 4, 71 for telephone calls that is provided for each button telephone T1 to Tn and is sequentially connected in series.
AC separation circuits 5, 8, terminal voltage detection circuits 6, 9, etc., and three types of impedance correction circuits 11 to 13 connected to switch groups 11 to dzK operated by a switch control unit 10 are provided, and key telephones T1 to The TrL includes a balancing network 15 connected to the 2-wire 4-wire circuit 14, a microphone amplifier 16, and a speaker amplifier.
A microphone 17 and a speaker 19 are provided, which are connected to a microphone amplifier 16 and a speaker amplifier 18, respectively. Note that FIG. 1 only illustrates representative elements necessary for explanation. The constituent elements are similarly provided in the other telephones T2 to Tn.

Further, the network 15 of the telephone TI is connected to other telephones T.
2 to Tn is designed to suit the case where the line length is the longest internal line distance specified by the button telephone device.

Three types of impedance correction circuits 1 provided in the main device 1
1 to 13 classify the distance between key telephones into short distance, medium distance, and long distance within the range of predetermined specifications;
~d2 is designed so that the impedance when each communication path and the impedance correction circuit are connected in series approximates the impedance of the longest internal line distance defined by the button telephone device. Therefore, the impedance correction circuits 11 to 13 are not a composite circuit of inductance, capacitance, and resistance, but may be approximately pure resistance.

Next, with reference to FIG. 1, the effects of representative elements will be explained. Telephones Tt-Tn are installed at a predetermined location and connected to the main device 1 through a communication path L1%Ln. By making the communication current a constant current, the communication current increases in proportion to the line resistance of the communication path. Ll
, L2 at the main device ends of the telephone constant current supply circuits 4, 7 are detected, the distance between the telephones TI, T2 and the main device 1 is calculated from the detected value, and the value is stored in the storage section 3. In the same way, continue this process up to the telephone Tn. Here, we will explain the case where the telephone T1 responds to an extension call from the telephone T2 by using the microphone 17 and speaker 19 without using the handset. do.

Now, when the telephones T1 to Tn are installed, the distance from the main device 1 is stored in the storage unit 3, so that the telephone T1 is connected to the telephone Tn.
When an extension call is received from 2, the control unit 2 reads the respective distances to the telephones TI and T2 from the storage unit 3 and adds them together, and the distances as a result of this addition are divided into the previously classified short distances,
It is determined whether the telephone T1. T2 communication path Ll, L
By closing the switch 1□s''2 to the 2, the connection is made through the AC separation circuits j15 and 8, and the switch b1 to d2 is connected to the corresponding impedance correction circuit among the three types of impedance correction circuits 11 to 13. 1
Close and connect pairs. In this state, the telephone Tl
The impedance of the line between T2 and T2 is approximated to the impedance of the line to which the balancing network is adapted.The input of the audio signal to the speaker amplifier 18 by the microphone amplifier 16 in the 2-wire/4-wire conversion circuit 14 is constant. can be kept to a low value.

As a result, the restrictions on the distance between the main device and the key telephone and the volume of the microphone and speaker from the balance aspect of the balancing network have been significantly eased compared to conventional key telephone devices, and the restrictions on inter-extension communication have been significantly eased. Since the impedance of the line is equivalently always long distance,
The volume of an internal call does not become extremely loud compared to the volume of an external call, and is always at a constant level.

〔Effect of the invention〕

According to the present invention, the line impedance during mutual communication between extensions of the button telephone device can be equivalently approximated to the impedance of the longest extension distance specified by the button telephone device, so that it is possible to Limitations on the distance between the main device and key telephones and limitations on microphone and speaker volume caused by the balance aspect of the balancing network attached to the 2-wire 4-wire conversion circuit for making calls between key telephones have been significantly eased, and the limitations on the volume of the microphone and speaker have been significantly relaxed. It is possible to eliminate extreme differences in volume between internal and external lines.

BRIEF DESCRIPTION OF THE DRAWINGS The figure is a block diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Main device, 2...Control unit, 3...Storage unit, 4.7...Telephone constant current supply circuit, 5.8...
・AC separation circuit, 6, 9...terminal voltage detection circuit, 1
0... Life switch control section, 11.12.13----
Impedance correction circuit, 14... 2-wire 4-wire conversion circuit, 15... Balancing network, 1611
...Mike Anne 7', 17...Mike, 18...
・・Speaker amplifier, 19・・・Speaker, Ts~T
fi@fist...button telephone, L1~Ln...call path.

Claims (1)

[Claims] In a button telephone device in which a plurality of button telephones are installed to compensate for calls by microphone and speaker using a balancing network, and each button telephone is connected to the main device by a communication path, the button telephone has a maximum length specified for the button telephone device. The main device is equipped with a balancing network adapted to the extension distance, and the main device includes means for detecting a terminal voltage due to a constant communication current at the main device end of the communication path, and calculating and storing the distance between the main device and each button telephone. Means for reading out this stored distance during any internal intercommunication between the microphone and speaker, correcting the impedance between each button telephone set connected in series via the main device, and adapting the impedance to the impedance of the distance corresponding to the balancing network. A button telephone device comprising: