So, you’ve looked up a phone and the corded compat for Leitner says: COMPAT UNKNOWN Here’s what it means. 1) If the Customer has an RJ9 sized HEADSET jack AND a Headset Button, then they should try the Leitner Quick Disconnect Cord! They should make a few test calls to figure out what compat combo in the cord is best for their phone. If they’re tried all the compat and it still isn’t working or doesn’t sound good, then head to Step 2. 2) If they do NOT have an RJ9 sized Headset Jack AND a Headset Button, OR if they have both of these but it still isn’t sound great, then they will need an amplifier! The good news is that Leitner corded headsets works with every brand of amp that we carry! See THIS ARTICLE foe more info on Leitner corded headsets and amps! In ALL cases, please GUARANTEE COMPATIBILITY and make sure the Customer is confident that if it doesn’t work properly, we will make sure they get something that does! And, please, if you find something that works, email compat@headset…