Building a receiver to flash light when phone is ringing?

Hi, is it easy to build a receiver that will activate the light when the phone rings? For example, something similar to :


http://www.sonicalert.com/htm/receiver.htm





Of course I can buy one but I will probably need to modify it to make it work with cordless phones in walkie-talkie mode (without needing a phone line). Thanks.Building a receiver to flash light when phone is ringing?
You can get these for under $10.00 for normal phones


http://www.nextag.com/phone-ringer-light鈥?/a>





But you said you would need to modify it for a cordless phone in ';walkie-talkie'; mode.. IF the cordless phone still connects to a phone line then any one of the ringers above will still work.





IF however, you need to put it on the phone itself that is a different issue. The cordless phone will not have the voltage from the phone line to ';ring'; it. It uses a different circuit. In most cases you would need a copy of the phone schematic to find WHERE inside the phone voltage is applied when it ';rings'; (many of these are audio circuits and not real ringers at all) If there is voltage applied when it ';rings'; you can just attach a light that is at the same voltage level at that point and your done. You may need to contact the phone mfg. for help or a print. Many of them have these as accessory items.