JPH0361736U

JPH0361736U -

Info

Publication number: JPH0361736U
Application number: JP12258989U
Authority: JP
Priority date: 1989-10-19
Filing date: 1989-10-19
Publication date: 1991-06-17

Description

[Brief explanation of drawings]

第１図は本考案ダイヤルトーン検出装置を実施
した電話端末装置の回路結線図、第２図は本考案
のダイヤルトーン検出装置の回路構成図、第３図
イ，ロ，ハは第２図のａ，ｂ，ｃ点における信号
波形グラフ、第４図は従来のダイヤルトーン検出
回路を含む電話端末装置の回路結線図である。１……直流変換器、２……フツクスイツチ、３
……２−４線変換器、４……ダイヤルトーン検出
装置、６……ダイヤルキー、７……ＤＴＭＦ発生
器、８……送受話器、４１……オペアンプ、４２
……比較器。 Fig. 1 is a circuit wiring diagram of a telephone terminal device implementing the dial tone detection device of the present invention, Fig. 2 is a circuit configuration diagram of the dial tone detection device of the present invention, and Fig. 3 A, B, and C are the same as those in Fig. 2. The signal waveform graph at points a, b, and c in FIG. 4 is a circuit connection diagram of a telephone terminal device including a conventional dial tone detection circuit. 1...DC converter, 2...Hook switch, 3
... 2-4 wire converter, 4 ... dial tone detection device, 6 ... dial key, 7 ... DTMF generator, 8 ... handset, 41 ... operational amplifier, 42
...Comparator.

Claims

[Scope of utility model registration request]

A device installed at a terminal of a telephone line that detects the tone of a selection signal emitted by an exchange when a subscriber's telephone goes off-hook, and functions as a bandpass filter upon receiving the signal from the telephone line entering the handset. It is equipped with an operational amplifier, a positive feedback comparator which also functions as waveform shaping by inputting a reference voltage that shares the power supply of the operational amplifier, and a voltage that varies the amount of hysteresis by means of adjusting the output of the operational amplifier. 1. A dial tone detection device characterized in that the output frequency is checked by a CPU, and when the output frequency is higher than a reference level and is a regular frequency, a dial tone is sent from a DTMF generator to a telephone line.