Talk about determined!!

11 Jan 2004
Reaction score
United Kingdom
Add on for caller line indicator
Starting with a Binatone Clip 100 Caller Line Indicator

I wished to add a home-brew to to indicate when the
caller has "Withheld" his number and the "Unavailable" situation
so i don't even have to break away from whatever i'm doing to view the
display let alone lift the receiver for more junk.
Unavailable - usually foreign callers .
That is using the BT FSK toneburst that precedes the
fiirst ring pulses. These units decode the info and display
the caller's telephone number (if not disabled).
I now know I'm being plagued by random tele-sales
calls generated by computer. That is bastard systems dial
out multi-lines by computer and if anyone picks-up the receiver
the system switches to a sub-'human' for the sales-call.
If these bastards are all tied-up doing their speal then the line
goes dead when i pick it up. A growing problem in the UK
and presumably elsewhere as well.
I know i will lose a few genuine UK callers ,who for
whatever reason have disabled the ident of their phone ,but I consider
retaining my sanity of more importance. I've taken a
spare one of these CLI units apart and there are 36 finger
contacts to the multiplexed LCD display - lower row of 14 large digits
,an upper row of smaller digits for time,incrementing count ,date
and other annotations.
For display -WITHHELD- a uniquely identifying sitiuation is
3rd digit central horiz. bar present and
4th digit absence of top horiz. bar of the alphanumeric letter W
For display -UNAVAILABLE-
1st digit present central horiz. bar is unique
The microcontroller is epoxied over so inaccessible.
Driving the LCD from an af generator about 80Hz and
about 3V pk-pk square wave. Too high a voltage and
extra segments light, too high f and too feint and
too low f then flickers. Also for determination the lines 29 to 36
on the pcb show a different DVM "diode test" value ,
back to the micro ,to
ground, compared to the 1 to 28 lines (LCD disconnected).
The LCD has 8 back-planes,
(numbering on pcb) lines 29 to 36.
33 to 36 relate to the (9 and 2 half) small digits and legends
29 to 32 the 14 large digits
For first 3 large digits and segments a to g (a at top ,then
clockwise) and an extra
double vertical segment (h) giving central segment of W.
( The double segment 5h is angled to give the right hand V
segment of unaVailable and I of wIthheld as not full alphanumeric dispaly )
Control 'matrix' (for just lines 1 to 6 and 29 to 32 and digits 1 to 3)
**/1 ,2, 3, 4, 5, 6,
lines 7 to 28 for remaining digits 4 to 14
For the UK anyway (digits 1and 2 blank) digit 3 only shows 0 for first digit
of disclosed
numbers so segment 3g off , 3g on only for the first - of "-WITHHELD-" and
first 2 digits blank.
the 1g segment is always off except for the first - of "-UNAVAILABLE-"
As far as i can readup for multiplexed LCDs segments only 'light'
when the timed stepwise voltages between BP and segment
exceed some threshold
folowed by the reverse phase of this voltage.Then relying on
persistence to maintain till the next cycle if still driven.
For all other smaller differences in drive voltages
they stay unlit. To avoid doing timing circuits would it be possible
to construct simple analogue differential amplifier
monitoring lines 31 and 2 for
'unavailable' and 31 and 6 for 'withheld'.?
Just one phase sense ,say BP greater than segment by 2.2V or whatever
(set on test),
and ignore the the reverse phase which is only there to keep
the liquid crystal happy, as far as i know.
Integrated outputs each gating one of 2 tones or patterns on a sounder,
heard between the rings of the phone.
On second thoughts i will choose 4h (pcb lines 30 and 8 ) as
the identifier of the vertical W segment
of WITHHELD (AND the 5h 'I' of 'withheld' ) ,
and 5h ( pcb lines 30 and 10) V of unaVailable
as i seem to remember,very rarely, some displayed
long mobile phone numbers use all 14 digits for the
number of the phone so a 2,3,4,5,6,8 or 9 there would
falsely register as withheld or unavailable.
Contrast is achieved by drive voltage, for 4V
battery supply
Contrast level 8 extreme output levels 0 to 4V
level 4 ,levels 1 to 4V
level 1,levels 1.6V to 4V
Eventually made just a cut down version.
Just decoded lines 10 and 30 to give a buzz for
unavailable and withheld situations only.
Both lines and battery connections to an external
box. Single rail quad op-amp, 10 and 30 lines to 2 window
comparators, integrator and piezo driver from Hex buffer pack.
The level shift pots may be problematic with
battery voltage drop.
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Sounds fine.
Although I love analog electronics, I may have a more elegant solution if the problem becomes more general.
For less than a fiver you could buy a pic 16F872 or similar, and by hijacking as many of the display lines as you like, you could program it to recognize far more patterns than just withheld, and either generate sounds (either for you or the phone line) or flash lights as required. Once some simple 'if the bit pattern is this then do that, else loop' type code has been written, it is an easy matter to 'tweak' it for other situations.
regards M.

Of course, you should already be listed with the TPS and that at least stops UK based companies pestering you.
Here's a nice bit of kit that works with BT's Home Highway called the Robson Micro PBX.

It has a nice facility to reject callers especially those still left in the UK using a bogus CLI. It can also reject witheld CLI.

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home highway kinda sucks though

line rental is more than two seperate analog phone lines iirc

and you still have to pay call charges or pay seperately for an unmetered dialup package.

frankly i see very few situations where its a good deal.

imo its only worth even considering if you either have a specialist need or can't get real broadband.

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