perfectHOHdevice

You need to get sound to your ears from the following sources:

1. Ambient sound - voices, phone ringers, car horns, etc. Sound that is is in the air.
2. Telephone handsets. Desk and wall phones almost always use a 4p4c jack and plug combination, sometimes called RJ9. It is smaller than the RJ11/RJ14 plug which goes from phone to wall.
3. Stereo radios, MP3 players, iPods, etc, tend to use a 3.5mm TRS plug/jack wired to this headphone schematic. In this configuration, any connected headset microphone does not work. Tip= left, ring=right, sleeve=ground.
4. Cellphones and cordless phones often use a 3-conductor tip/ring/sleeve (TRS) plug and jack combination in 2.5mm or 3.5mm (1/8 inch) size. They will be wired according to this headset schematic, so the left channel goes to both ears and the microphone is active. Tip=left, ring=mic, sleeve=ground.
5. Some cellphones, especially smartphone or PDA phones that can play music, will use a 4-conductor 2.5mm TRS plug/jack combination. Here is a schematic. Tip=left, ring1=right, ring2=mic, sleeve=ground. Sometimes a momentary switch is wired ring2 and sleeve, to serve as an 'answer phone' button. Nokia cellphones may use a different schematic.  

Now I have the Oticon Epoq and Streamer. It allows input to my HAs via two mechanisms:

1. Bluetooth. The Streamer serves as the microphone, and the HAs are the left and right speakers. I am not certain whether I am getting true stereo sound, or just the same signal sent to both ears. I don't honestly care that much!
2. 2.5mm, 3-conductor plug. In this configuration the microphone is not active. Again, not sure if sound is stereo or mono, but it is in both ears. An adapter can easily allow plugin to a 3.5mm jack, and indeed the Streamer comes with just such a cord (2.5mm on one end, 3.5mm on the other).

I want to be able to use the streamer with more devices - especially with desk phones and cellphones. And it would be nice to have a wireless hookup to stereo inputs. So I need a device that works kinda like this:

 concept device

 rough schematic

Places for parts and peices:

• http://www.oldphones.com/servlet/Categories?category=PARTS
• Shows how to wire standard handset to a cellphone plug.
• Jabra BT headset and desktop hub

Input/Output:

• 2.5mm 2-ring (tip=speaker, middle=mic, sleeve=ground)
• 2.5mm 3-ring
• 3.5mm 2-ring (dual jacks; microphone and speaker)
• RJ11 phone
• RJ14 phone handset
• Bluetooth
• telecoil (hearing loop) builtin
• microphone ... switchable omnidirectional/cardoid pattern
• headphone output
• vibrating alert (signalled by door or other presence sensors)

Sound meter?

Similar (but incomplete) devices: SoundWizard II, Comfort Duett