JPS5862957A - Extension hand free response circuit - Google Patents

Abstract

PURPOSE:To assure sufficient transmission level and to simplify the circuit constitution, by realizing the function for loudspeaker reception of main trunk and extension hand free response, and assuring suitable reception sound volume to the functions. CONSTITUTION:A plurality of button telephone sets KT are connected to a main device ME with a pair of channels SL and a pair of control lines DL, a hand-set HD is connected to a channel SC of the main device ME, and a changeover relay SR changes over the channel SL to the circuit SC and a coupling transformer T. The output of the transformer T is separated at a hybrid circuit HYB, one is given to a speaker circuit S with an attenuator ATT and another is given to a microphone circuit M. A control circuit KC of the telephone set KT is connected to the control line DL to control the relay SR, the attenuator ATT and the circuit M with a signal from the telephone set KT and a speaker button SK. The functions of the loudspeaker reception of the main trunk and the extension hand free response are realized, allowing to ensure suitable reception sound volume for the both.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention provides a button telephone device that responds to a voice call from an extension through an extension hand (7), a response ring (Kl), which is built into the 'd1 telephone in addition to the handset, and which responds to a voice call from an extension.
I do it.

The functionality of the FiIiik#t button phone has become more advanced, with the ability to answer and talk to voice calls from extensions without having to pick up the handset, using the built-in microphone of the phone.
That is, a hands-free response is provided. Typical circuits to achieve this are audio switch circuits and hybrid circuits. Although the voice switch path has high performance, the circuit configuration is complex and it is difficult to realize it economically.

On the other hand, a no-brid circuit has a simple circuit configuration and is highly economical, but has drawbacks such as a small feedback residual.

If the use of the hybrid circuit is limited to internal calls,
Although the hybrid balance mismatch is relatively small, the amount of O side ttjIc'& from the microphone to the speaker is still small, making it impossible to ensure sufficient transmitting and receiving volumes.

In particular, when the amplifier circuit for the speaker is also used for loudspeaker reception of the central office line, Ef1, the axis of variation d of the input signal level of the central office line.
#Because of the wide area, it was necessary to increase the gain of the amplifier circuit), and in order to prevent howling, the gain of the amplifier circuit for the microphone input could not be increased, making it impossible to achieve sufficient speech performance.

In order to solve the above-mentioned problem, the present invention makes the gain of the speaker amplifier circuit variable between the loudspeaker reception state and the hand-free response state, and will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which a main device MEK and a plurality of telephones KT (only one is shown in the figure) are connected in a star shape by a pair of communication lines SL and a pair of control lines DLK, respectively. ing. A central office line CO is also connected to the main device ME. The handset HD is attached to one side of the telephone call circuit 80.
is connected, and the switching relay BRK and the communication line SL are switched and connected to the other side of the communication circuit SC and the coupling transformer 〒. The coupling transformer T separates the direct current of the speech line SL and supplies the voice signal to the hybrid circuit HYIIK. Speaker a via hybrid circuit HYB K damping circuit Ti
SS is connected again! Iklophone m*w4/・Ibrid 1ro IfflKm! It is threaded. The speaker circuit 8 includes a speaker 8P, a speaker amplification path S 10, and a micro-amplification path M! 411 from the Iku four-phone MIC and microphone-phone amplifier circuit MAK. The control circuit, KC, operates the loudspeaker button 8, not shown in the figure, based on information from the dial button, central station, extension selection button Nakakogo 11DL, etc., in a manner similar to that of button telephone 4D61111111. is used.

(from the hybrid circuit HYI Hirokata 8L) The audio input via the lance T is supplied to the speaker circuit 8, the signal from the microphone circuit M is supplied to the communication line ttL, and! The previous issue is suppressed from being transmitted from the four-phone circuit M to the speaker circuit 8.

Relay 8R is normally closed and communication circuit 8CIIK is closed.
Sending and receiving 1a HD calls are possible. For loudspeaker reception, the 8R relay connects the transformer TIIK and the hybrid circuit [B and call 1118L.

'K to receive amplified sound is to press the loudspeaker button 8 on the telephone KT.
Press K. This is K) The control circuit KC drives the relay SR, closes the output to the transformer i side, and connects the switch M8 t-14 inserted in series between the microphone MIC and the microphone four-phone amplification circuit M. and attenuation circuit T
Let the amount of surface reduction of T be zero. At this time, the audio signal on the communication line SL is amplified with sufficient gain and is emitted from the speaker SP.

On the other hand, when a voice call occurs, incoming call information is transmitted from the main device ME to the control circuit KC via the control line DL.

As a result, the control line KC drives the relay SR, closes the contact to the transformer TIRE (closes the switch MS: and attenuates the input to the speaker circuit S from the attenuation circuit ATTK. As a result, the signal from the microphone MIC is transmitted to the microphone It is amplified by the amplifier circuit MA and sent to the telephone line SL through the hybrid circuit HYB.The signal on the telephone line SL is also supplied to the speaker circuit SK via the hybrid circuit HYII and the attenuation circuit ATT, and is emitted from the speaker SP. Ru.

In the case of hand-free response, the benefit of the speaker system (attenuation circuit M'I"rsP and speaker circuit 8) is lower than that of loudspeaker reception.
ed decreases, but it is limited to the signal-like extension call signal input from the call line SL, and a sufficient signal level can be ensured, so there is little reduction in the volume of the voice emitted (from the speaker 8P). In addition, since the gain of the microphone/phone circuit y can be increased in accordance with the decrease in the gain O of the speaker system, the level of speech transmitted to the communication line BL can be increased and the communication performance can be improved.

By configuring the control circuit KC with a built-in microcomputer, the attenuation circuit TT as described above can be obtained.

Control of the switch MS can be easily achieved by determining various states based on various information at the time and setting the switch MS to a predetermined state.

As explained above, according to the hands-free response circuit of the present invention, it is possible to realize the functions of loudspeaker reception of the central office line and extension hands-free response with a simple single circuit configuration, to secure appropriate reception volume for each, and to In the latter case, a sufficient transmitting level can be ensured.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an extension hand-free response circuit according to the present invention. ME: Main equipment, KT: Telephone, CO: Office line, SL=Speech line, DL=Control line, SR: Switching relay, SC: Speech circuit, HYII: Hybrid circuit, MUTT: Attenuation circuit,
S: speaker circuit, M: miter circuit, KC: control circuit,
SK: Loudspeaker button. Patent applicant Nippon Telegraph and Telephone Public Corporation agent Military expenses Taku

Claims (1)

[Claims] A speaker circuit, a Microhoff circuit, and a microphone circuit for supplying an audio signal inputted from the communication line to the speaker circuit, supplying a water audio signal input from the microphone circuit to the communication line, and supplying the audio signal input from the microphone circuit to the communication line; - a hybrid circuit for suppressing interference signals from the speaker circuit to the speaker circuit; A button telephone capable of taking a response state and a loudspeaker receiving state in which a call signal from a central office line is heard through the speaker circuit, comprising: an attenuation circuit inserted between the I/ibrid circuit and the speaker circuit; - means for reducing the amount of attenuation of the attenuation circuit in the extension call response state to a greater extent than in the amplified voice receiving state.