Caller ID - Part 3
Part three of the Caller ID project details a simple enhancement to kill unwanted calls.
See Part One of this project for the Caller ID hardware interface,
and Part Two of this project for the Caller ID data format and software requirements.
What use is having your PC know who is calling you if it can't do something about those unwanted nuisance calls - the international call centres, the double-glazing salesman, the tax man, your ex, etc? This simple modification uses the DTR line from the PC serial port to pick up the call and kill it.
This doesn't need much explanation. The Caller ID software is responsible for determining if the call is wanted or not. If not, the software asserts the DTR line for a couple of seconds. This turns on the transistor and energises the relay, which loads the line as if a telephone was answered.
The exact components depend on what you have lying around. At the time of constructing this, I was using a 5v PSU for the Caller ID and only had 12v DIL reed relays to hand. So I added a 5v to 12v DC/DC converter to give me the supply for the relay. If you are buying parts for the project, I'm sure you can do better and source a DIL reed relay that operates at the same voltage as your supply!
The most pleasing part about all this is that the caller ID information is sent before the first ring signal is sent, so unwanted calls can be killed without the phone even ringing! (The caller will hear a single ring followed by a click... and then silence...)
The example CallerID application includes the necessary code to detect and kill unwanted calls.
This software is licensed under the CC-GNU GPL.
Use, modification and redistribution of this software is free of charge, however some rights are reserved
and license conditions apply.
What use is having your PC know who is calling you if it can't do something about those unwanted nuisance calls - the international call centres, the double-glazing salesman, the tax man, your ex, etc? This simple modification uses the DTR line from the PC serial port to pick up the call and kill it.
Circuit Enhancement
This doesn't need much explanation. The Caller ID software is responsible for determining if the call is wanted or not. If not, the software asserts the DTR line for a couple of seconds. This turns on the transistor and energises the relay, which loads the line as if a telephone was answered.
The exact components depend on what you have lying around. At the time of constructing this, I was using a 5v PSU for the Caller ID and only had 12v DIL reed relays to hand. So I added a 5v to 12v DC/DC converter to give me the supply for the relay. If you are buying parts for the project, I'm sure you can do better and source a DIL reed relay that operates at the same voltage as your supply!
The most pleasing part about all this is that the caller ID information is sent before the first ring signal is sent, so unwanted calls can be killed without the phone even ringing! (The caller will hear a single ring followed by a click... and then silence...)
Software
The example CallerID application includes the necessary code to detect and kill unwanted calls.
This software is licensed under the CC-GNU GPL.
Use, modification and redistribution of this software is free of charge, however some rights are reserved
and license conditions apply.There is no charge for this software. It is licensed under the CC-GNU GPL.
I am happy to receive comments on this project. Due to its nature, however, I am unable to offer support if you have problems making it work.