Ring Detection & Count

Ok i have found this interesting ring detection circuit from:

Detecting a telephone RING 1 Electronic Circuit - CircuitsArchive

As it is well explained, the first circuit detects ringing but i want to be able to count the number of rings that occured as well as ring detection so that i could open the telephone line when the specified ring count is reached in order to control the activation of an electrical device using the telephone keypad.

I found the attached article which uses the 4N25 Opto-Coupler for Ring detection just like the link above but it also incorporates ring counting. I don't understand how the counting is obtained from the circuit. It is referred to as the Optic Isolation unit in the article. I thought after reading the 4N25 datasheet, all that is needed at the output of the Opto-Coupler is a pull up resistor of about 10K depending on the incoming ringing voltage. However, i notice four resistors together with a transistor at the output of the 4N25 in this attached article.

Are those four resistors and transistor used to determine ring count?...And if so, could someone please explain it to me like how the ring detection is explained in the above link (i.e. why is each of the four resistor is used and the transistor so i could calculate my own values for my design project). I would appreciate it very very very much.

Regards.

dramrattan said:

I found the attached article which uses the 4N25 Opto-Coupler for Ring detection just like the link above but it also incorporates ring counting. I don't understand how the counting is obtained from the circuit. It is referred to as the Optic Isolation unit in the article. I thought after reading the 4N25 datasheet, all that is needed at the output of the Opto-Coupler is a pull up resistor of about 10K depending on the incoming ringing voltage. However, i notice four resistors together with a transistor at the output of the 4N25 in this attached article.

Are those four resistors and transistor used to determine ring count?...And if so, could someone please explain it to me like how the ring detection is explained in the above link (i.e. why is each of the four resistor is used and the transistor so i could calculate my own values for my design project). I would appreciate it very very very much.

Regards.

Click to expand...

hi,
The resistor values will be the same for the 4N25, they are to produce a +5V pulse from the low level signal from the 4N25.
The PIC requires that the pulse be 0 to 5V.
The counting is done within the PIC.

The first question to ask is:
Do you want to use a microcontroller in any part of your circuit?

About using Microcontroller

Yes i intend to use the PIC18F452 so i guess i could use the ring detection circuit from the link as the iunput to the 4N25 opto-coupler and the four resistors together with the transistor at the output to facilitate the PIC18F452 requirement of 0-5V input right?

Just use the simple circuit I use in my Infinity Bug. It counts the rings by comparing with a delay. To open up the infinity bug, you ring 3 times then hang up. Then ring again after 40 seconds.
You can produce all sorts of different combinations with simple delay circuits.

Infinity Bug

I did a search for the Infinity Bug and didn't see anything. Where is the link about this infinity bug project?

<snip: spam link> left index: Infinity Bug

Infinity bug

Thanks got it.

the infinity bug given in the above link will not activate the phone directly. is there any way to stop the phone from ringing? i mean when we dial the number and also send a tone immediately(use a tone decoder), can we get connected directly?not that i want to do something illegal,just for educational purpose.
i studied different techniques like hook switch bypass,third wire etc. i also want to build the infinity bug. please tell me how to do it.

Sorry, it's the no-ring Infinity bug that has the ring detection. I have not posted the no-ring version on the web.

The posted version is called the Simple Infinity Bug.

On the simple version you can see a 1N4148 picks up the ring pulses above 90v, and prevents the bug from detecting the ring.
You can use the same principle of detecting the ring and feeding it into a 74C14 and make an output go either high or LOW.
This output then has a 100k and 100u time-delay circuit that feeds into another Schmitt Trigger to give you a timing after 4, 5, 6 rings etc. It's as easy as that.

thank you very much Mr.colin! another small request. is there anyway to send the tone along with number dialed to activate the phone? i mean i will send a tone immediately after i dial the number, and it should trip the ringer in the phone and pick up the line. any ideas? thank you once again!

To get the infinity bug to pck up the line you simply send 5 rings then hang up for 40 seconds and re-ring the line.
The receiving circuit detects the 5 rings and not more than 8 rings. It then waits for a re-ring within the period 30 seconds to 60 seconds.

Mr.colin, i understand and thanks! we ring 5 times and again after 30 seconds.will the distant phone ring?if it does, can't we bypass the ringer and pick the line directly? Manny Mittleman achieved this feat many years ago through his 'harmonica bug'. i want to do it too.please give me some circuit ideas.

Ring times vary amongst countries, so I do not think making a preset delay is best. Why not make ring detect software detect ring until ring stops for say x time then consider that as a ring, or end of ring if you will. This way ring detection is country independent.

Detecting the sound of the 5 rings is my secret and you have to buy the No-Ring Infinity Bug for $250.00 to find out how it is done.

I do NOT like this circuit AT ALL !!!!

The so-called "ground" is DIRECTLY tied to one side of the LINE !

Remember guys: A phone line should be treated the SAME way as an Hydro line.

YOU NEED ISOLATION !!!!

If there's no transformer, relay or optocoupler or at the limit, a half watter high voltage 10 meg resistor, don't play around with it !

And in a ring detect circuit for a phone line, the input capacitor MUST be a 250 or 400 volt non-polarized (plastic) capacitor ( 0.1 to 2.2 uF will be okay), next, you need some kind of AC voltage detection with a fairly LOW sensitivity. A ringing voltage is 90 VRMS 20 Hz sinewave surimposed to the open line (48VV) voltage. So your ring detect must be triggered by the 90 VAC but NOT by the 0 dBm voice signal. Voltage dividers and Zeners are welcome here, but FIRST AND BEFORE ALL, an optocoupler is a MUST ! And do noot forget the optocoupler's LED protection (reverse polarity)

Hope that will help !




Hope that will help !

Colin doesn't care much about legality or safety apparently. Mind you the operation of such a device is illegal in a great many places.

I don't know which circuit is being talked about, however you can listen to these "armchair technicians” all day and you will find they have not produced one single circuit on the internet.
I have sold hundreds of Infinity Bugs both as kits and made-up and only 15 people have died using them. I am waiting for 25 people to get electrocuted before I withdraw them from the market.
You will find most phones have no isolation from the phone line as many of them charge the internal battery from the line by taking pulses of heavy current for very short periods of time.
The infinity bug is isolated from the outside world as it is heat-shrunk and nothing is exposed.
In addition, these devices are not illegal as they do not intercept the conversation on the phone line, so don’t take any account of any "armchair technician,” they really don’t have a clue about anything and they will never provide you with anything constructive.

Colin, hundreds of people have bought the circuit, how many have successfully assembled and implemented it? And just because you're not intercepting a phone call doesn't make it legal. In many places you can't record or tap into the audio of someone else without their direct consent.

is there really a chance of getting electrocuted with this circuit? if i place the circuit in a plastic box,will it help?