US 4,536,619 A · Ringing signal detection circuit

Abstract

A ringing signal detection circuit for a subscriber's apparatus which is connected to a telephone office line together with an attached telephone set. An incoming signal on the telephone line is converted to a pulse signal with a repetition frequency twice the incoming signal by a full-wave rectifier and a differentiating circuit. The pulse signal is applied to a retriggerable mono-stable multivibrator through a photo-coupler and an inverter. The time period of a metastable state of the multivibrator by one trigger pulse is selected to be longer than the break period in the dial pulse signal but longer than a half cycle of the ringing signal. Therefore, the multivibrator is maintained at the high level for a longer time period at a time when the incoming signal is the ringing signal than the time when the incoming signal is the dial pulse signal. Therefore, the ringing signal can be detected from the time period when the high level signal is continuously maintained and distinctly distinguished from the dial pulse signal. The time period of the high level signal can be detected by the use of a clock pulse generator, an AND gate to which the high level signal and the clock pulse are applied, and a pulse counter connected to the output of the AND gate. The time period is, thus, represented by the number counted in the counter.

Drawings

Drawings are temporarily unavailable. Open the PDF at USPTO

Drawings

Claims8

Dependent claims

A ringing signal detection circuit for a subscriber's apparatus connected to a telephone office line together with a telephone set having a rotary dialling device for sending out a dial pulse signal, which comprises;

first means receiving an incoming signal on the telephone office line and producing a pulse signal with a repetition frequency twice that of the incoming signal:
second means coupled to an output of said first means and providing a high level signal at an output thereof in response to each pulse from said first means, said second means maintaining the high level signal continuously during a time period when pulses are applied thereto with a pulse interval smaller than a predetermined break period in the dial pulse signal;
and
third means for detecting a time period during which the output of said second means is maintained at a high level, said third means providing a ringing signal detection output at a time when the detected time period is equal to a predetermined time period in relation to the ringing signal,
said third means comprising:
clock pulse generator means for generating clock pulses at a predetermined repetition frequency higher than the dial pulse signal;
fourth means coupled with the output of said second means and said clock pulse generator means for permitting the clock pulses to pass therethrough during a time period when the output signal from said second means is maintained at the high level;
and
counter means coupled with an output of said third means and counting up the clock pulses passing through said fourth means, said counter means providing the ringing signal detection output at a time when a counter number in said counter means is equal to a value predetermined in relation to the ringing signal.

6 more elements

Dependencies are inferred from the claim text.

Description3,400 words

Summary1,225 words

#This invention relates to ringing signal detection circuits for subscriber's apparatus each being used together with a telephone set for an office line.

#In the present specification, the terms of the subscriber's apparatus includes a facsimile device, a telephone automatic answering device, a key-telephone-system control unit, a direct connection telephone set and all other apparatus or devices which has ringing signal detection circuits and which are used together with telephone sets to common office lines.

#In those apparatus, when a dialling device is operated at the attached telephone set for calling another party, the ringing signal detection circuit of the subscriber's apparatus and the attached telephone set are connected to a common office line. Therefore, the dial pulse signal sent out from the attached telephone set is also applied to the ringing signal detection circuit of the apparatus.

Brief description of the drawings6 figures

#FIG. 1 is a view for illustrating a circuit diagram of an embodiment according to this invention;

#FIG. 2 is a view for illustrating signal waveforms at various points in the circuit of FIG. 1, to explain operation of the circuit in response to the incoming ringing signal;

#FIG. 3 is a view for illustrating signal waveforms at various points in the circuit of FIG. 1, to explain operation of the circuit in response to the incoming dial pulse signal;

Detailed description2,016 words

#Referring to FIG. 1, a subscriber's apparatus 1 such as a facsimile device is connected to an office line l together with a telephone set 2. The apparatus 1 includes a ringing signal detection circuit, a load impedance 3 such as a resistor connected to office line and other functional portion. The functional portion is not shown because the present invention relates not to the functional portion but to the ringing signal detection circuit.

#The ringing signal detection circuit comprises a DC-cut capacitor 11 and a rectifier circuit 12 having four diodes, which are connected in the connecting circuit between the office line l and load impedance 3. A light emission diode portion 13 of a photocoupler is also connected in the circuit connecting rectifier circuit 12 and data input and output circuit 3. An output of a photo-transistor portion 14 of the photo-coupler is connected to an inverter 15, an output of which is coupled with a retriggerable mono-stable multivibrator 16 having a predetermined metastable time period. As well known in the art, the retriggerable mono-stable multivibrator is a type wherein when an input pulse is applied to the multivibrator which is in its mestastable condition, the multivibrator is retriggered to start a new metastable state. The metastable state is selected to be longer than a half cycle of the ringing signal but shorter than a break period in the dial pulse signal. An output of multivibrator 16 is applied to one of the input terminals of an AND gate 18, while clock pulses from a clock pulse oscillator 17 are applied to the other input terminal of AND gate 18.

#Operation of the ringing signal detection circuit will be described hereinafter, referring to FIGS. 2 and 3 in addition to FIG. 1.

Facts

Application

06/565,629Filed 27 Dec 1983

Priority

JP 57-22772828 Dec 1982

Granted

20 Aug 1985

Term ended

27 Dec 2003

Estimated · how

Pre-1995 term; greater of 17 years from grant or 20 years from filing when eligible. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification4 codes

H04M 19/04
Providing ringing current or supervisory tones, e.g. dialling tone or busy tone: the ringing-current being generated at the substations
F02B 2075/025
Having less than six strokes per cycle: two
H04M
Telephonic communication
F02B
Internal-combustion piston engines

Ringing signal detection circuit

Life of this patent

Ringing signal detection circuit

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims8

Description3,400 words

Drawings

Classification4 codes

Life of this patent

Description3,400 words