Phone line interface - works with new transformer
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Posts: 46,084
Well, I had suspicions about the transformer. I replaced the one I
got from DIGI-KEY with one fro RadioShack and it works great.
The are both supposed to be 600 ohm phone coupling transformers but
obviously something was screwy. The DC resistance was similar but
who knows.
Thanks for your help Stephan!
--- In basicstamps@yahoogroups.com, "Stephen H Chapman"
<chapman@t...> wrote:
> The fact you are not breaking dial tone with the BS2 interface
means the
> Central Office did not hear your DTMF signals, or invalid digits
were
> received and ignored by the CO DTMF register. Dial tone is removed
from the
> line after the first digit is received in the register. A
requirement of the
> transformer you selected is the winding facing the CO line should
be able
> to accept 20 ma to 100 ma of line current and not have the
transformer
> inductance saturate because of the DC line current.
> A requirement of the CO register for DTMF signals is to have the
DTMF tone
> present for a minimum of 40 millisecond and then a interdigital
40 ms
> silent interval.
> It is necessary to use the .001uf capacitor across the transformer
secondary
> to bypass the high frequency components. Hope this helps.
>
Original Message
> From: "rczapala" <rczapala@y...>
> To: <basicstamps@yahoogroups.com>
> Sent: Thursday, April 01, 2004 12:04 PM
> Subject: [noparse][[/noparse]basicstamps] Re: Phone line interface
>
>
> > Thanks for your reply Stephen.
> >
> > Yes, touch tone phones work. After I know the BS2 has dialed, I
pick
> > up the phone and there is still a dial tone. If I then hit the
reset
> > on the stamp board, I can here the tones over the phone, but the
> > dial tone remains. If I hit one of the phone buttons, the dial
tone
> > stops when the phone system recognizes the tone generated by the
> > phone.
> >
> > I used a transformer from Digi-Key (MT4112-ND) instead of the
Jameco
> > (117760) but they are both 600 ohm telephone coupling
transformers.
> >
> > --- In basicstamps@yahoogroups.com, "Stephen H Chapman"
> > <chapman@t...> wrote:
> > > Does a touch tone telephone work on the telephone line you are
> > testing the
> > > BS2 circuit?
> > > You should use the following sequence of operations. Close the
> > relay
> > > contacts to make the phone circuit in an off hook state. Wait 2
> > seconds for
> > > dial tone signal from the Central Office. After dial tone
signal
> > is heard
> > > then you can go into a DTMF signalling mode. The circuit does
work.
> > >
Original Message
> > > From: "rczapala" <rczapala@y...>
> > > To: <basicstamps@yahoogroups.com>
> > > Sent: Thursday, April 01, 2004 6:52 AM
> > > Subject: [noparse][[/noparse]basicstamps] Phone line interface
> > >
> > >
> > > > Hello everyone!
> > > >
> > > > I built the phone line interface described in the "Basic
Stamp II
> > > > Applications Notes" manual (using the 600 ohm transformer,
> > Sidactor,
> > > > zener diodes, etc).
> > > > The DTMFOUT instruction is generating tones, but the phone
system
> > > > does not recognize them - I continue to get a dial tone. I
stuck
> > a
> > > > transistor in the circuit to amplify the volume slightly,
but to
> > no
> > > > avail.
> > > > I also tried varying the DTMFOUT ontime and offtime
parameters -
> > > > again no luck.
> > > >
> > > > Anybody have any suggestions? I am using the BS2 chip.
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > To UNSUBSCRIBE, just send mail to:
> > > > basicstamps-unsubscribe@yahoogroups.com
> > > > from the same email address that you subscribed. Text in the
> > Subject and
> > > Body of the message will be ignored.
> > > >
> > > > Yahoo! Groups Links
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> >
> >
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the
Subject and
> Body of the message will be ignored.
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >
got from DIGI-KEY with one fro RadioShack and it works great.
The are both supposed to be 600 ohm phone coupling transformers but
obviously something was screwy. The DC resistance was similar but
who knows.
Thanks for your help Stephan!
--- In basicstamps@yahoogroups.com, "Stephen H Chapman"
<chapman@t...> wrote:
> The fact you are not breaking dial tone with the BS2 interface
means the
> Central Office did not hear your DTMF signals, or invalid digits
were
> received and ignored by the CO DTMF register. Dial tone is removed
from the
> line after the first digit is received in the register. A
requirement of the
> transformer you selected is the winding facing the CO line should
be able
> to accept 20 ma to 100 ma of line current and not have the
transformer
> inductance saturate because of the DC line current.
> A requirement of the CO register for DTMF signals is to have the
DTMF tone
> present for a minimum of 40 millisecond and then a interdigital
40 ms
> silent interval.
> It is necessary to use the .001uf capacitor across the transformer
secondary
> to bypass the high frequency components. Hope this helps.
>
Original Message
> From: "rczapala" <rczapala@y...>
> To: <basicstamps@yahoogroups.com>
> Sent: Thursday, April 01, 2004 12:04 PM
> Subject: [noparse][[/noparse]basicstamps] Re: Phone line interface
>
>
> > Thanks for your reply Stephen.
> >
> > Yes, touch tone phones work. After I know the BS2 has dialed, I
pick
> > up the phone and there is still a dial tone. If I then hit the
reset
> > on the stamp board, I can here the tones over the phone, but the
> > dial tone remains. If I hit one of the phone buttons, the dial
tone
> > stops when the phone system recognizes the tone generated by the
> > phone.
> >
> > I used a transformer from Digi-Key (MT4112-ND) instead of the
Jameco
> > (117760) but they are both 600 ohm telephone coupling
transformers.
> >
> > --- In basicstamps@yahoogroups.com, "Stephen H Chapman"
> > <chapman@t...> wrote:
> > > Does a touch tone telephone work on the telephone line you are
> > testing the
> > > BS2 circuit?
> > > You should use the following sequence of operations. Close the
> > relay
> > > contacts to make the phone circuit in an off hook state. Wait 2
> > seconds for
> > > dial tone signal from the Central Office. After dial tone
signal
> > is heard
> > > then you can go into a DTMF signalling mode. The circuit does
work.
> > >
Original Message
> > > From: "rczapala" <rczapala@y...>
> > > To: <basicstamps@yahoogroups.com>
> > > Sent: Thursday, April 01, 2004 6:52 AM
> > > Subject: [noparse][[/noparse]basicstamps] Phone line interface
> > >
> > >
> > > > Hello everyone!
> > > >
> > > > I built the phone line interface described in the "Basic
Stamp II
> > > > Applications Notes" manual (using the 600 ohm transformer,
> > Sidactor,
> > > > zener diodes, etc).
> > > > The DTMFOUT instruction is generating tones, but the phone
system
> > > > does not recognize them - I continue to get a dial tone. I
stuck
> > a
> > > > transistor in the circuit to amplify the volume slightly,
but to
> > no
> > > > avail.
> > > > I also tried varying the DTMFOUT ontime and offtime
parameters -
> > > > again no luck.
> > > >
> > > > Anybody have any suggestions? I am using the BS2 chip.
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > To UNSUBSCRIBE, just send mail to:
> > > > basicstamps-unsubscribe@yahoogroups.com
> > > > from the same email address that you subscribed. Text in the
> > Subject and
> > > Body of the message will be ignored.
> > > >
> > > > Yahoo! Groups Links
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> >
> >
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the
Subject and
> Body of the message will be ignored.
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >