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Ringing Tone Detector for Minimizing Wrong Number Disturbance

IP.com Disclosure Number: IPCOM000084330D
Original Publication Date: 1975-Oct-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 3 page(s) / 27K

Publishing Venue

IBM

Related People

Shepherd, PJ: AUTHOR

Abstract

Automatic communication terminals, for example, automatic facsimile terminals, can be arranged to set up calls over the switched telephone network without operator assistance. Wrong number annoyance can be minimized by including within the transmitting terminal a ringing tone detector, to detect whether the receiving apparatus responds within a predetermined time by counting the number of bursts of ringing tone.

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Ringing Tone Detector for Minimizing Wrong Number Disturbance

Automatic communication terminals, for example, automatic facsimile terminals, can be arranged to set up calls over the switched telephone network without operator assistance. Wrong number annoyance can be minimized by including within the transmitting terminal a ringing tone detector, to detect whether the receiving apparatus responds within a predetermined time by counting the number of bursts of ringing tone.

It is assumed that if more than this predetermined number of bursts are detected, then the wrong connection has been made: it would be expected that an automatic receiving apparatus would respond very quickly. At least two bursts of ringing tone need to be detected to ensure that at least one burst of ringing current has been received by the receiving terminal, because of the multiphase nature of ringing current generation.

Most countries have ringing tones between 390 Hz and 460 Hz, and it is expected that all countries will eventually have ringing tones between 400 and 450 Hz. It is also expected that cadence will have a minimum value of 0.67 and 2 seconds on and off, respectively, and a maximum value of 4 and 6 seconds on and off, respectively. At the present time however cadence varies considerably from country to country, but in nearly all countries no ringing tone in present use has an off period of less than 2 seconds. This characteristic enables ringing tone to be distinguished from other tones present on the international telephone network.

Fig. 1 shows a ringing tone detector and decoder. Bandpass filter BF passes signals with frequencies between 390 and 460 Hz through operational amplifier AMP having a gain of 20, to ensure that the signa...