SparkFun Forums

[vinodquilon]

Look up the attachment.
http://www.scribd.com/doc/27392525

When power up the circuit all LED s 1 to 4 turned-on (I expect all turn-off).
The problem is that, When I calling from remote end all the LED s blinking randomly for 1 sec (undesired result) and then
comes to a stable state.

But this blinking effect doesn't exist when I manually turn-on the circuit after passing first ring.
Now all LED s directly comes to the stable state without blinking as narrated below in the table.

The surprise attack is that depending upon the service provider of telephoning remote person the
stable state varies as indicated below:

OPERATOR(India) LED4 LED3 LED2 LED1

BSNL OFF ON OFF OFF

VODAFONE OFF ON OFF ON

IDEA ON OFF ON OFF

RELIANCE ON OFF OFF ON

AIRTEL OFF OFF ON OFF

Local land-line end working on BSNL line.

I doesn't believe in the supernatural effects, but there should be an evil influence.javascript:emoticon(':evil:')

I also tried the TOE in of DTMF IC, but after enabling DTMF Outs (after passing first ring) the
first state would be the stable state described above without blinking problems. PWDN pin also not working.

At a time subsequent to this stable state, DTMF IC obeys the normal truth table specified in the MITEL data sheet
upon different key events on remote end after off-hooking local end.

This is the third IC I have replaced, first two ones- MT8870CE,35P050C9,9004 AE
didn't work at all. Third one- MT8870CE,12579.2,9125 AE- have the above issues. Next time I will choose KT3170 !!!javascript:emoticon(':roll:')

Without solving these issues I can implement my project by,
1. Designing a ring counter which turn on the circuit only after passing first ring, thus no blinking problems at all.
2. Designing a tri-state buffer with decoder at output of DTMF IC. Thus #<decimal> key combination can be designed.
Circuit designed to turn on trisate for 5 sec when # key presses. During this interval I can press a decimal key,
which is assigned to a particular house-hold device. Thus turn on-off corresponding devices. One of 16 outputs of
Decoder IC will turn on at a time depends on DTMF BCD outs.

First time I didn't notice this stable state changes between different operators as
in my workbench I have been using my personnel mobile phone as remote end and land line in my home as local end.
When I switched to my friends' mobile having different connection I noticed this change. javascript:emoticon(':oops:')

[markaren1]

see your previous post and read the recommendations.

http://www.epanorama.net/circuits/teleinterface.html

The circuit you describe should not be attached to a phone network...

-Mark

[vinodquilon]

The circuit you describe should not be attached to a phone network...

-Mark[/quote]

Why did you say the above quote ? javascript:emoticon(':?:')

[riden]

The problem is that, When I calling from remote end all the LED s blinking randomly for 1 sec (undesired result) and then
comes to a stable state.

Caller ID signaling?

[vinodquilon]

The problem is that, When I calling from remote end all the LED s blinking randomly for 1 sec (undesired result) and then
comes to a stable state.

Caller ID signaling?

Exactly, in India CLIP signals are in DTMF format and occurs between
first and second rings for 1 sec duration.

[riden]

I'm not sure exactly what you want to do, but I think you want to be able to call into this device and have it decode your DTMF tones sent by the caller. If that is the case, the device should only be activated when the phone is answered. This presumes that your device isn't doing the answering. If my understanding is correct, I would add an off-hook detector and have that control the INH line of the 8870 in such a way that the 8870 is inactive until the phone is answered. That is about all the specific advice that I can give as it has been year since I've built and used telephone interfaces. Things surely have changed a lot since then. A little more research on your end and you should have the problem solved.

[vinodquilon]

I'm not sure exactly what you want to do, but I think you want to be able to call into this device and have it decode your DTMF tones sent by the caller. If that is the case, the device should only be activated when the phone is answered. This presumes that your device isn't doing the answering. If my understanding is correct, I would add an off-hook detector and have that control the INH line of the 8870 in such a way that the 8870 is inactive until the phone is answered. That is about all the specific advice that I can give as it has been year since I've built and used telephone interfaces. Things surely have changed a lot since then. A little more research on your end and you should have the problem solved.

Not INH pin, but PWDN pin of 8870 should be used for enabling 8870
after off-hook. INH only inhibits the detection of alphabet characters.

[riden]

Not INH pin, but PWDN pin of 8870 should be used for enabling 8870 after off-hook. INH only inhibits the detection of alphabet characters.

Thanks for the correction. I confess that I didn't consult the datasheet and assumed that it inhibited the detection.

[Acecare]

I'm not sure exactly what you want to do, but I think you want to be able to call into this device and have it decode your DTMF tones sent by the caller. If that is the case, the device should only be activated when the phone is answered. This presumes that your device isn't doing the answering. If my understanding is correct, I would add an off-hook detector and have that control the INH line of the 8870 in such a way that the 8870 is inactive until the phone is answered. That is about all the specific advice that I can give as it has been year since I've built and used telephone interfaces. Things surely have changed a lot since then. A little more research on your end and you should have the problem solved.

I definitely agree with you riden. Actually, it's been a long I am using telephone and I don't encountered this problem. I think as time passing by, there are many changes happen in their mode.