Batboard

Hi, I have a DM1550LS and want to connect three headsets single ear at the accessory port at the back of the radio, but don't know the safe impedance allowed. can some one help me on that? does 8ohoms and higher is ok? thanks

What brand/model of headsets are you using? Sigtronics? David Clark? Fire Com?

If you use the speaker out put the audio is 'floating' bridge circuit that can not be grounded less you blowout the audio amplifier stage in the radio.

So an isolation transformer is needed.

There is a filtered audio output that could be used that is not affected by the radio's volume control. But you will need an simple amplifier to drive the headphones.