The resistor value is not critical. You could probably use 1k resistors. It’s just that 600 ohms is a fairly common audio impedance. If the device being fed has a high input impedance (say 10k or more) then 1k would be as fine as anything else.
Beer is always a good idea ))) But, seriously, I’ll be in Antwerpen in the middle of June…
Peter, regarding diodes, is it not nessesary to protect line-out from reverse current?
(in Peter’s place): negative (haha); diodes are about direct current and audio signals are alternating current. The resistors are sufficient to limit currents to acceptable values, even in case of a short circuit.
And I’ll be very happy to welcome you to my native town, keep me posted if you will.
Thank you, Jan, for both explanation and welcoming :) I’ll be back with results…
To get rid of doubts I’ve also contacted MHOxygen, as one of devices will be O2D2. It has 1K output impedance. So, I’ve used 60ohm resistor for it and 1K for iPhone/iPad device.
And, of course, heatshrinked :)
Works great.
Excellent. What kind of annunciation does the O2D2 give? I didn’t know it had such a feature 
From manual:
FLOW-FAULT EVENT: Red Light flashing on and off with Hi-Lo audio chime for ~ 2 seconds with every event.
APNEA EVENT: Flashing Amber Light four (4) discrete times with audio beeps once every four (4) seconds until unit detects
a valid inhalation event
OK, but presumably these are the same annunciations which I can already hear anyway even with the headset on. They are loud enough.
