some weird effect of Telephone DTMF MT8870CE !!!

[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.
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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 !!!
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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:replaceText('%20;D',%20document.forms.postmodify.message);