This circuit, connected to my sound card and a set of cordless phones, seems to be the cheapest way to talk with my computer wirelessly around the house.
The design is mostly from http://www.grynx.com/projects/build-your-own-chat-cord/ Improvements are welcome. The parts, especially the line isolation transformer, can be scavenged from a cordless phone. My local Goodwill sells them for $5. The microphone and speaker connections, at the right, are to those jacks in a sound card.
The 9V can come from a battery. That worked for me until I experimented with leaving a muted speakerphone on for hours. Now I use a 9V power supply. It caused a hum on the phones, but the capacitor and the resistor (the left one) filter it well enough.
I'm using a digital cordless phone but there's still noise. What are the likely causes? Wires too long? Lack of shielding?
Have you tried alternatives?
Unfortunately, phones give the computer no easy way to indicate that it wants to talk. It could ring the phone, but that's a more complicated circuit - and annoying. Instead, when my computer has something it wants me to hear, it shows messages on the TVs.
©2004-2008 Patrick Roberts | Burlington, Ontario, Canada