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USR.MOD
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Text File
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1996-03-03
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5KB
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130 lines
=================================================================
HARDWARE MODIFICATIONS
=================================================================
Seeing as there have been requests via netmail for more information about
the motherboard upgrade to allow the CID information through on the older
motherboard/daughterboard Couriers, here's the information that's
available:
_ _ _ O / _ _ C_U_T_ H_E_R_E_ _ _ _
O \
first order Caller ID service from your phone company, and you must install
the Flash ROM upgrade.
Parts needed:
(1) Resistor, 10K ohms, 1/4 watt
Any garden-variety carbon resistor will work just fine.
(1) Capacitor, .033 uF, 200 volts minimum
Old-fashioned ceramic disk parts should be OK, but a mica or polyester
part would be preferred. Do not use any sort of polarized or
electrolytic part. Capacitors must be rated at 200 volts or better!
Solder one lead from each part together, connecting them in series. Keep
the lead lengths short, the parts should be close together. Polarity does
not matter.
Solder here and
trim leads short ---> X
/X\
/ \
/ \
--- ---
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| R | | C |
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--- ---
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There are 2 different circuit board layouts for the USR motherboard. The
location that you will install this little circuit depends on whether you
have the REV "E" motherboard or an earlier one. The REV "E" motherboard is
easy to spot because of the "REV E" etched into the board at the front
corner, between the end of the volume control slider, and the front panel
push-switch. Also, the REV "E" board has the speaker located in the rear,
near the serial port connector. On earlier boards, the speaker is located
more towards the middle of the board.
In either case, the R-C circuit needs to be installed so that it jumpers
2 pins on one of the motherboard chips. This is a small 6-pin chip that
is used as a solid-state hookswitch relay. On the REV E boards, the chip
is an LH1500 or XCA111, and is designated U11. On earlier boards, the
chip is an LH1056, and is designated U8.
In both cases, the chip is located near the DIP switch block. Look
at the silk-screened lettering on the board, and you will see that all
the component locations are marked. Just look for U8 or U11 as needed,
and make sure the part number stamped on top of the chip matches the ones
listed here.
Pins 4 and 6 of this chip are the "relay contacts". Solder the free
ends of the series R-C circuit across pins 4 and 6 of the chip. It doesn't
matter which end goes where, as long as the circuit is "jumpering" those
2 pins.
BEFORE SOLDERING, BEND AND TRIM THE LEADS TO MAKE THEM AS SHORT AND NEAT
AS POSSIBLE. AVOID SPILLING SOLDER ALL OVER THE PLACE, AND DON'T
OVERHEAT ANY OF THE COMPONENTS!
Top view of chip The chip will have a notch or a dot molded
into the plastic to indicate the location of
pin #1.
----\/----
|* |
1 --| |-- 6 <------\
| | \
| LH1500 | \
2 --| LH1056 |-- 5 ------ The R-C circuit "jumpers"
| XCA111 | / these 2 pins. (4 and 6)
| | /
3 --| |-- 4 <------/
| |
----------
That's all there is to it! Now put the modem back together, load the
Caller ID flash rom, and you're in business. Don't forget that Caller
ID info comes in between the first and second rings, so you have to set
up your software to allow 2 rings before answering! And be sure that
you reset all the factory settings with AT&F1&W. The Caller ID flash
rom adds new s-registers to the modem, and these will contain "garbage"
values until you do the complete reset.
If the Caller ID detection is unreliable, you can try changing the values of
the 2 components. Resistor values can range from 1K to 100K and capacitor
values range from .0033 to .047 uF. Try various combinations to see what
works best for you.
THIS MODIFICATION IS NOT NEEDED ON THE SINGLE-BOARD MODEMS! The newer
design uses a real mechanical relay, and it already has these 2 parts
installed across the relay contacts.
End of File.
_ _ _ O / _ _ C_U_T_ H_E_R_E_ _ _ _
O \
The parts used were from R.P. Electronics and total cost was about 80 cents
for an axial lead Mylar capacitor (0.033 uF) and a 10K resistor.