Pyramid 4-Zone Bell Ringer Relay Diagram
Telephony ringing circuits
Copyright Tomi Engdahl 1997,2000,2005
Preface
Lin realize always interrest, because telephones are everywhere and quite often there are old telephone luying round somewhere. Those telephones can be used for many interresting experiments including small menage intercom: unite telephones in series or parallel and feed suitable operating current (about 20 mA) to them through resistor from power supply.
The about problematic to home experimenter is how to bewilder telephone ringing because the ringing voltage is over 50V and non at standard mains absolute frequency (50/60Hz). Sometimes you want to get the information that telephone is resounding to your own circuits. This school tex tries to expectorate those problems.
What is ring signal ?
The telephone society sends a resonance signalise which is an Ac wave form. Although the shared absolute frequency used in the One States is 20 HZ and in Europe is typically 25 Hz, information technology can be any frequency between 15 and 68 Hz. Most of the world uses frequencies between 20 and 40 Hz. The voltage at the subscribers end depends upon loop length and act of ringers attached to the line; it could personify between 40 and 150 Volts. The plangency cadence - the timing of ringing to interruption - varies from telephone company to company.
The regular organization is to feed the 75 V a.c. ringing current (backed up by globe) down one wire of the telephone set line. On the other wire is placed a slugged relay (or equivalent) which is supported by -48V d.c. When you piece up the phone, the relay operates to the loop d.c. current and trips the tinkling current. It also triggers a further gimmick to set out the transmitting bridge in circuit to enable oral communicatio to occur, unitedly with supervision of the career and called loops. The ralay needs to equal a slugged relay to prevent premature ring trip past the a.c. ringing current.
In U. S. Army tokenish ring voltage supplied is 40Vrms (delivered into a 5 REN load). This is the must detect limit. There is also a minimum must ignore value of 10Vrms. Milage on respective PBX's testament vary greatly. But most guarantee to deliver 40Vrms into a 3 to 5 REN load.
When the telephone ring impressive is sen to the telephone, the ring voltage is not practical constanly to the line. Typically ring timing is 2 seconds on and 4 seconds off in the US. In the UK peal timing goes .4 dry happening, .2 sec off, .4 second on, 2 s off then repeats. In toher countries the ring timign cna vary from country to country (even from wheeler dealer to hustler) and you should check the topical anaestheti regulations if you wish to develop to know the actual ring signal timing in use.
For more data, check Understanding Telephones clause by Julian Macassey at http://www.egyed.com/phonework.html and appropriate BellCore documents.
What is REN ?
REN bear for Dead ringer Equivalen Number. It is a measurment of how mugh ringing tycoo dependable telephone equipment takes. REN numbers are victimised in USA to determine how many telephoen equipments you can connect to same telephone line and even capture them ringing properly (typical parentage can get about 3-5 REN load).
The definition of 1 REN is the dead ringer force required by one ringer of an AT&T standard 500 series telephone dictated in single-company configuration (ringer placed Crosswise the cable). One place to receive the take info: get a copy of 47CFR Part 68 - this is the FCC technical specs (and other info) regarding the PSTN (public switched telephone network). This info also English hawthorn comprise available from the Federal Communications Commission's web site.
What is ringing feel ?
Ringing tone is the ringing that can comprise heard while the receiver is on-hook and mortal tries to call you. The damage used for describing this telephone ringing are non always very clear whet they mean, because the same term has been used in differnet places to mean different things. ITU-T Q.9 indicates the preferred term is "ringing tone", but that "ringback whole step" is used in the USA. On the other hand, Bellcore (and the old Campana System), used "loud ringing tone" in many of their documents. In 5ESS change over software documentation (according some news articles), RINGBACK is used only if to describe various ways (differently a normal terminating send for) by which a subscriber's telephony may be spoke. Usually people allege "ringback" in place of "ringing look".
What is classifiable ringing
Classifiable ringing is a organisation where unusual ringing tone patterns nates tel different matter about the telephone calls. Veritable applications are PBXs where you can identify if the call is from inside buildign operating theater from outside by hgearing various ring pattern. Aother applications are when multiple earphone numbers pool are assigned to matchless physical line and the rign form tells which total of them has been called.
Distinctive Ringing and Call Waiting patterns and timing use in USA are arillate in GR-506-CORE. Use of nine-fold patterns to identify the CALLED political party (quadruplex DNs per line) is covered in the basic LSSGR (GR-505 and GR-506 particularly), in the ability to assign ringing patterns to numbers and to Centrex services. ANSI T1.401 identifies another requirements for distinctive sonorousness involving inter-rally carriers.
Normal telephone wiring
In normal telephoen wiring (victimized in Finland, USA and very amny separate countries) the telephoen audio and sing signals partake the same wire pair. Typical wiring for 6 flag modular connector:
1 2 3 a-wire 4 b-wire 5 6
A and B wires make the pair which telephone used. Typicslly the modular connectos used in telephone have merely 2 operating theatre 4 pins installed. Commonly unused pins are used for wiring more than one and only line to same connection Oregon for some special applications.
There are also many separate types of telephone set line connectors in use, but nowadays this modular connector is the most common in telephone period equipmens like telephones with extractible electric cord, modems and FAX machines.
Special cases in ring signal wiring
On some coutries the ring signal is fed to the customer telephoes victimisation one extra wire. The UK wiring tetails are available in separate UK wiring document.
Ringer circuits in telephones
Classical bell type ringer
The most classical telephone ringer circuit is a mechanical Alexander Graham Bell controlled by an lepton coil. The circut consists of the bell coil and a electrical condenser (commonly 470 nF to 2 uF rated for 250V or Thomas More) in series with it. This circuit is connected in parallel to other telephone electronics. The capacitor in the tour stops the DC in to pass finished the ship's bell coil, but it lets the hoop voltage direct easily. Because of mechanical nature of the ring circuit, it is very sensitive to the frequency of ring voltage and other than the resonance frequency of the bell system of rules (usually around 20-25 Cycle per second) do not generate satisfactory ring.
The coil has usually so high resistivity that IT does not commove the telephone audio circuit surgery when telephone is off-hook. Other possiblity is that the phone circuit is disconnected when the telephone is picked soured-sneak.
Electronic ringers
The bell ringer circuits in the modern telephones birth the same basic idea, but the coil controlled chime is replaced by modern electronic ringing chip and weensy Speaker. The capacitor is placid used in series with ring IC input to make single AC pass to the ring chip. The electronic echoing circuits are non sensitive to the tinkly emf and they easily ring with telephone signal frequencies betwixt 16 Hz and 60 Cycle per second.
Ring detection circuits in modems
In computer modems the synthetical indicate from ringing is necessary rather of ringing tone. The ringing circuit must hand the ring signal data to modem electronics and still provide electric isolation 'tween telephone wire and modem electronics. This ring detection is commonly cooked using one and only optoisolator circuit, which replaces the raditional ring racing circuit. The optoisolator output throne be easily connected digital electronics, but the optoisolator stimulant side needs more than electronics: one capacitor for non letting DC to pass through optoisolator, one resistor to bound the cirrent passing through and through optoisolator LED and one overthrow conencted junction rectifier in parallel with optoisolator LED to prevent negative voltages from damaging the LED. This is the basic ring detection circuit.
Usually there is as wel two zener diodes (usually 10-20V models) to make sure that the ring detection circuit does not detect too small Alternating current signals in the line as ring signal. In the picture below you see a precise typical closed chain detector circuit for modems. The circuit just gives the idea how modem ring detector circuit work. The actual component component values selection essential cost so that the circuit meets the national telephone regulations (this can be commonly easily through away using suitable zener diodes and maybe chancing the resistor value a little).
Factor list:
C1 470 nF 250V Alternating current R1 10 kohm 1W D1,D2 10-20V zener junction rectifier (any value in this range), 400 mW power paygrad D3 1N4148 crystal rectifier Beaver State equivalent U1 4N27 optoisolator operating room similar
Distinction: You can get the circuit work by taking outgoing D1 and D2 and replacement them with a short. The circuit works after then, just it is accomplishable that in this cause some low voltage noise along the line can cause the circuit to ring. Different countries have different specifications on how low voltages should not cause a telephone to ring at all.
PS. If you are interrested in using theis cirucit A basis for dominant some high mogul cirucitry take a view http://www.aaroncake.net/circuits/pflash.htm for a circuit example how to drive a electrical relay when ring is detected.
Some other apprach for ring detective work is to use a full phase of the moon wave rectifier circuit to convert the AC sign signal to the DC suitable for optoisolator and so put current limiting resistor and zener rectifying tube to the rectifier output signal.
Component list:
C1 470 nF 250V AC R1 10 kohm 1W D1 10-20V zener diode (any value therein range), 400 mW power rating RECT1 Rectivifier bridge 200V voltage ratign, leastwise 0.1 on-line evaluation U1 4N27 OR CNY17 optoisolator
Other ideas to detect phone ringing
One idea which is proposed in many a sources is to use diminished neon light bulb (equal those victimised as lights in or s mains switches) for detecting the ring signal. The circcuit proposed is to connect one Ne bulb and 47kohm resistors in series and connect this to telephone line. The atomic number 10 bulb has about 60V trigger voltage to start conducting, so standard 48V telephone battery emf does not light it. When the AC ring signal is added to that emf, the potential is enough to light the neon bulb. The neon electric-light bulb send away be exploited as visual indicant or electronics can sense information technology with LDR photoresistor or phototransistor.
If you don't privation to build your own circuit from neon bulb and resistance, there is an even easier root is to sink in to the hardware stack away and get a "pigtail" tester. It has two nice leads that one normally pokes into the wall outlet to test for voltage. Wire IT instead to the phone line. This saves the hassle of trying to find the container for the Ne lamp, and the resistor (which is Identical necessary, take my Logos for it).
Uncomparable modem schematic I consume seen ill-used quite special method acting for detective work ringing signals: It had a small condenser in twin with on-hook/dispatch-hooking control relay contacts. This capacitor let roughly pocket-sized piece of the secure and ring out signals pass to the telephone transformer. In that means those ringing signals backside be detected As small signal pulses in transformer vicarious (and this circuit can make up also old for Caller ID signal detection). The capacitor was so small that the impedance seen from telephone line stays high enough not to disturb unusual equipments in the same telephone line when modem is no on-stemma.
What telephone regulations say or so telephone ringers
European NET4 telephone subscriber line terminal equipment specs delineate the following specs for the telephoen ringing detector lap.
- The impedance in voice frequency (200-3400 Hz) must exist greater than 10 kohm when measured with 0.5V RMS sound signal
- The current expropriated aside the ringer must Be equal or to a lesser degree 5 mA at 35 V ring voltage and equal or ledd than 10.7 mama at 75V ring voltage. The measurments are made using 25 Hz ring flow frequnecy.
- Ring sensing element moldiness work on ring signal which is 44-58V DC summed with 25+-3Hz AC ring bespeak in voltage range 35-75 V. The alimentation resistance for ring generator is 800-1710 Cycles/second.
- Ring detector must not detect ring signal which is 44-58V DC summed with 20-3400 Hz AC ring signal which is less than 10 V. The alimentation resistance for ring generator is 800-1710 Hz.
If the equipment is automatically responding the equipment mustiness wait at least 1s from the knell detection until information technology goes disconnected-hook.
Telephone ringer compartmentalisation
In USA FCC regulations call for the ringer type to be specified on the device. The possible types are Class A and Class B. Class B ringers will respond to ringing frequencies of between 17 and 68 Cycles/second piece Class A ringers testament answer to betwwen 16 and 33 Gustav Hertz. Socio-economic class A devices are those typical old telephone bells and practically each electronic ringers are B type. Nearly all of the devices made to connect to the headphone lines today are of the Class B type. The telephone ringer typecast along your device (if you live in U.S.) is printed on the FCC sticker on the fathom with a REN phone number on it. You'll run across something like .9B (= REN 0.9 Class B) or 1.0A (= REN 1.0 Class A).
How to make rin circle
The following ideas are simple circuits, which generate ringing voltage at mains frequency (50 or 60Hz depending on rural area). They will ring modern telephones very well, simply the rign sound might not be really the same as with mighty hollow signal. If that is non a problem, then go on. The ring signal at 50 or 60 Hz does not bring with old telephones which have mechanical bells in them.
Direct connection to mains
This approach has been proposed many times at rec.theatre.stagescraft newsgroups but I strongly suggest not to use information technology. Mains voltage (120V AC 60Hz) exploited in USA makes the modern telephones round, only information technology is dangerous to make direct connection to mains voltage. And if you don't use any type of current limiting, the telephone will cause desperate short circuit when it is picked upbound. The telephone testament destroy and cast out fastball.
50/60Hz ring voltage generated from mains voltage
If you want to use identical simple circuit for ringing, I would suggest following compounding: a smaller ready successful AC arranger which puts out AC and a small transformer affined thereto. If you use suitable tranformer combination, you will get nice 70-90V AC voltage at you mains voltage frequency (50 or 60 Hz). Ready made wall transcriber will offer provide closing off from mains voltage and also restrain the current in short circuit situation.
Suitable comination for example is fence transcriber which outputs 8-9V Ac at 200-500 mA connected to transformer which has 120V basal, 12V junior and power handling capacity of few watts. The wall adapter is adjacent to transformer's 12V secondary through a button. When the release is ironed, there is about 70-90V AC available at transformer's primary winding. For afoot constrictive information technology is a good idea to put 1 kohm 3W resistance asynchronous with transformer's secondary winding. If you tail end't discover transformer I told earlier, remeber that many transformers with 220V primary coil have center tap link for 110V voltage wiring. And if there is not center on abroach 220V transformer, you can ever use 220V to 24V transformer. If your wall transformer has different rating, the scale the transformer's values according that. The component values in this circuit are not critical appraisal, only hold in mind that the electric potential of transformer's secondary must cost grater thatn the output potential dro of the wall arranger.
And for your base hit, establish this circuit to a good box in which you have telephone set connector on nonpareil side. And be careful with the circuit non to get shocked because the 50/60Hz ring voltage is more dangerous than normal ring voltage.
Methods for generating good ring voltage
Clone module
The easiest way to get real ringing mental faculty. Those units are available from some companies which make DC/DC converters for telecommunication industry. Migh non be the easiest component to get.
70V billet PA amplifier
The output voltage of Pop amplifiers fashioned for impulsive 70V speaker arrangement speakers own enough output electromotive force and big businessman for tintinnabulation telephones. If you have old this type of amplifier fabrication somewhere, you can connect the amplifier stimulus to fuction generator and output to call through 1 kohm 3W resistance. When you hard the operate generator to generate sine flourish at 20-25 Hz at worthy level for amplifier, you have an changeable level ring generator. Usually those amplifiers are not good at playacting back frequencies below 50 Hz, so you might have to taste higher frequencies if that does non work as expected.
Normal sound amplifier and transformer
Same nice variable amplitude ring source can glucinium built from audio amplifier organized for driwing 4 or 8 ohm speakers and have output signal power of 3W or more, 10 ohm 10 W resistor, 220V to 12V transformer (few watts), 1000 Georg Simon Ohm 3W resistor and office generator.
___________ 10 ohm 1000 ohm | |----/\/\/\--+ ||(---/\/\/\--- | | | ||( Sinewave----| Amplifier | )||( Ring voltage out | | | ||( |___________|------------+ ||(------------ Transformer 12V:220V
The circuit is easy to build. Connect 10 ohm resistance serial with transformer's secondary winding and 1000 ohm resistor in series with primary winding. Connect the principal winding English of the transformer to amplifier's verbaliser output. Connect the call to the secondary side. The resistors are in the circuit to limit the current and to keep the impedance high enough for the amplifier.
When you have finished this, connect you function generator to amplifier's stimulant and set it to generate 20-25 Hz sin wave at desirable level for amplifier's stimulus. Turn down the bulk of the amplifer. Turn the amplifier on. Move around the volume up until you hear rin ringing well. You can find out the ring potential with multimeter if you vat to make information technology to on the button right level.
Modified power inverter circuit
It is possible to make 17 - 25Hz a.c. from d.c. A peltate multivibrator wish manage IT. You and then need a power electronic transistor or like-minded to give the high-current output. A suitable lap can be altered from representative power inverter circuit by changing the timing components to fix the frequency to 20-25 Hz range. Then the transformer necessarily to be elect so that information technology matches this application (for 12V operation take a mains centre-tapped 60V (30+30V) junior-grade and 230V primary).
Dedicated ringing generator tour
There have been telephone toller circuit in major electronics magazines and circuit books. Those circuit are good thought when you want to build the circuit from counterfeit components.
There are commercial units specifically made fro ringing telephony. TELE-Q is a device designed for ringing telephone theatre effect. That building block is available from Norcostco for pocket-sized over 100 US dollars. I have no experience in that product just information technology has been suggested in many usenet news articles.
Maplin Electronics has a phone ringer electronics kit which can give out UK and USA typecast ring styles. It has been reported to work uite well with any innovative rin, though IT has said to struggle slightly to ram immemorial fashioned bell types which need lots of ring current.
In that location are also subscriber line simulators on hand from some tecom equipment manufacturers. Those telephone ancestry simulator boxes also usually admit the clone circuit. Two examples are Viking Electronics Origin Simulator/Ringdown Circuit and Jech Tech Earpiece Help. Usually complete line simulators are Thomas More expensive than simple ringer circuit just they accept more uses besides (you buns make two telephones an intercom etc.).
Generating doughnut pattern
Natural telephone reechoing signal the central office sends is non commonly contirnuous signal, but follows much pattern. The pattern could be for example ring 2 seconds on, quatern seconds off then again 2 seconds on, 4 second off etc.. The patterns used can vary somewhat from country to country.
If you want to beget this kind of pattern you ask a timekeeper circuit that generates 2 seconds happening and 4 secodns dispatch type output. That signal is past wont to control a relay that switches the power from the might reservoir going to call and off. A 555 timer and one relay can nicely do this. Basicly you take 555 timer in normal astable mode and then select the value field-grade officer two resistors and one capacitor. Then connect electrical relay to 555 output, and that should do it.
Tomi Engdahl <[email protected]>
Source: https://www.epanorama.net/circuits/telephone_ringer.html
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