CallerID Interface System
- Background and Overview:
- A while back we got DSL service that includes TV, and one
of its neat features that it integrates CallerID functionality.
When we get a call a little window pops up in the corner of
the TV screen displaying the name and number of the incoming call.
I thought the feature was neat, but not so useful since I don't
watch much television. One day I read that some modems can display
CallerID information and it occurred to me that I could create a
system to popup CallerID information on my computer. There are
a couple companies that offer similar products, but I'm a
cheapskate, and buying something is never as fun as building
it yourself anyway.
- The hardware consists of a modem attached to a serial port on
my home Intranet server, which is in turn connected to my other systems
via an Ethernet network. Software on the server monitors the modem's
output for CallerID information and uses the data to update a web page
and send a message to our PCs where it pops up on the screen.
- The Hardware Interface:
- The choice of modem is an important one since not all modems support
CallerID functionality. I'm using an old Zoom V.34 Faxmodem (VFX28.8)
I found after trying several models that didn't work. Many models
will not display CallerID information by default, and others will
claim to work but will sit like a brick as calls come in. The only
way to know for sure is to find a whole bunch of old modems (remember
that the speed doesn't matter) and sit down and fiddle with them all,
but that's the fun part, isn't it?
- The commands for my modem are:
- at#CID? - Display current mode, 0=Disable, 1=Formatted Output, 2=Raw Output
- at#CID=1 - Set the CallerID mode (in this case to 1 for Formatted Output.)
- The Software:
- The server software initializes the modem and then watches for
text coming from the modem. Here are the details of the interface
for my modem, your mileage might vary. Basically there are four
different possibilities that we need to catch. The word
RING is also displayed, but they are of no value in this
application. The four possibilities and what they look like follow,
note that the time and date are always displayed. If the phone
number is not available 0 is displayed, if the name isn't
available a code is displayed indicating that the name is either
unavailable or blocked.
- The first case is that the name and number are available.
- DATE = 0807
- TIME = 1719
- NMBR = 1234567890
- NAME = GEORGE BUSH
- The second case is that the number is available, but the name is
not for some reason. 0801 indicates that a code will follow,
4F is hex for O which means that the name field isn't available.
Also notice that the fourth field is labeled MESG instead of
NAME. (Thanks to Matthew Hallacy for help decoding this.)
- DATE = 0814
- TIME = 1958
- NMBR = 1234567890
- MESG = 08014F
- The third possibility is that the number is available, but the
caller has requested that their name be blocked or withheld.
We can tell that it's blocked by the message code 0801
again, but this time the code is 50 which is hex for P.
I haven't gotten many of these, so I'm not sure if the number is
- DATE = 0808
- TIME = 1751
- NMBR = 1234567890
- MESG = 080150
- The last case is that nothing is available, the number field is
zero and we get a not-available code.
- DATE = 0809
- TIME = 1535
- NMBR = O
- MESG = 08014F
- When the server gets the fourth field (NAME or MESG) it sends
the record in a delimited form to my clients via UDP packets.
The client IP addresses are just hard-coded into the application,
but since it's written as a Perl script it's easy to change.
The server also adds the record to the top of a web page if you
just want to keep a log of who's called. Since CallerID
information is sent from the phone switch during the pause between
the first and second rings and the web page is updated an instant
later it might even be possible to check the web page and see
who's calling while the phone is still ringing.
- The client software listens to the specified UDP port, undelimits
the data and display it. The Windows/Tk version displays a little
popup window like the one at the top of this page, the Macintosh
client just appends the record to the end of a list in the program
- Client and server code plus other bits are provided in the following
files. Both contain the same files, the ZIP file is simply provided for
the OS-challenged. It's all free, just remember where it came from. :-)
- All of my code was written in Perl,
which is a large part of why the whole project took only a couple evenings.
My server is based on FreeBSD,
some modifications may be needed for other systems, but that's your
job not mine... so stop emailing me about a Windows version.
- Note that the Windows/Tk version requires the Tk user interface
module for Perl, which can be found at the CPAN
- Ideas, Options, and Enhancements:
- Several people have asked how to duplicate the popup messages on
their televisions. I'm not sure, but it might be possible using an
inexpensive video overlay module like this one
I found a while back.
- In some cases we get the phone number but no name, esp. for people
from other parts of the country. And easy enhancement would be to
compare the phone number to a pre-defined list, and modify the
name (or 'unavailable' message) if the phone number is from a known source.
- I've toyed around with adding speech synthesis to announce the
incoming CallerID name using a text-to-speech package like
but I'll have to work on a home audio system first since my server
sits in the basement laundry room...
- If you only have Microsoft Windows clients to support you could use
'Windows Popup' messages to send the CallerID records instead of
running a client piece. These can be generated on Unix systems
using Samba's smbclient
utility with the -M option.
- Legal Mumbo-Jumbo:
- Feel free to download, use, distribute, and modify code found
on this page to suit your needs. I provide no support for
any of this though, so your on your own. This software has been
tested, but I am not responsible for anything that occurs to your
computer. Use at your own risk, yada, yada, yada.
Last Updated 1/26/2002 -