Ivo Zivkov • almost 9 years ago
Small Asterisk-based device
This can be done quite easily with a little device, which I will describe later. It operates like this:
1. The deice has 2 RJ11 jacks - one for the phone and the other to plug the device to the wall. The device is placed between the phone and and wall jack. This work best with a cordless phone, so all calls go through this device.
2. When a call is made, the device automatically answers the phone. No ring is generated to the phone, so the user does not hear the ringing.
3. The device plays a short messages, saying this phone is equipped with call blocking device. The device then asks the caller to press a number on their phone, say between 0 and 9. If the caller enters the correct number, the phone rings, and the receiving party can answer the call. If this is a robo-call, the number is never dialed, and the the device hang up the line. The home-owner is not aware of the robo-call at all.
4. If this is a valid live caller, the device "white-lists" this called ID, and next time they will be connected directly without a challenge.
5. The device can keep a list of valid auto-dialed numbers as well, such as 911 callbacks, etc. These calls will not be challenged.
6. There are other functions which can be performed by the device. For example the receiving party can black-list a caller even if it is a real person. For example if a marketer makes repeated calls, the callee can enter a code on their phone, and this number will be blocked in the future.
Description of the device:
The device consists of a small computer running Asterisk PBX software (http://www.asterisk.org/). Most of the above-described functionality is already available in the Asterisk. It requires a relatively small modification the Asterisk privacy manager function (http://www.voip-info.org/wiki/view/Asterisk+cmd+PrivacyManager).
The software can run on a low-cost computer boards, such as the $25 Raspberry PI (http://www.raspberrypi.org/). In addition, it needs 2 cards which provide connection to the phone system – one to the phone and one to the wall jack – these are called FXS and FXO. These boards can be manufactured for about $10 each. In mass production, the whole device could be produced for less then $50.
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