how can restricte access to '0' code in telephon line

[djavad]

hi
we have 1oo telephone line in our company that want to be restricted for users dialing "0"at first.
we wont do it from telephone center.
please help our
thank alot


[email protected]

 

[Asjad]

When you dial you send sound tones down the telephone line.

What you need is a notch filter which will remove the sound representing
the number '0'

if you goto:

https://www.frars.org.uk/cgi-bin/render.pl?pageid=1023

you will see that 941Hz represents the digit 0, if you remove this
then your problem will be resolved

I hope this helps!!

 

[Sebi]

In DTMF system always two tones representate a number...
But if You solved this problem locally (on each phone), the result is not complete, because with answering machine remote controller also possible dialing zero via microphone...

 

[fat-tony]

Except that will prevent you from dialing a phone number with a 0 in it (like 432-0194). You'll probably need a DTMF decoder of some kind, to block 0 until another tone is heard.

 

[gerty]

You could use a tone decoder with associated logic that if a 0 is pressed while a dialtone is present it would disconnect. That way it would be possible to dial a # with a 0 in it and not get disconnected since once you start dialing there is no dialtone. A simple and gate should do it.
dialtone+zero=disconnect..

 

[ljcox]

You could use a tone decoder with associated logic that if a 0 is pressed while a dialtone is present it would disconnect. That way it would be possible to dial a # with a 0 in it and not get disconnected since once you start dialing there is no dialtone. A simple and gate should do it.
dialtone+zero=disconnect..

Alternatively, you could analyse the first digit (this is necessary anyway and avoids the need to detect Dial Tone). If it is in the 1 to 9 range, you allow the call to proceed. If it is zero, then open the circuit to release the call and hold it open until the caller hangs up.

Have you considered pulse dialling? Some phones can be set to send either DTMF or decadic (ie. dial pulses). If so, then you need to detect if decadic pulses are received and, if so, open the circuit to release the call.

Decadic pulses are normally about 67 milliseconds in length (ie. the circuit is opened for that period)

Len

 

[fat-tony]

I really like that idea. Simply decode the first tone and go from there.

 

[Phasor]

I assume you have a PABX system installed. Most PABXs are programmable, so you can place any restriction you want. Just read the instruction manual :?