I'm trying to enable "barge in" on an NEC/Nitsuko 124i phone system, but cannot get it to work.

I've verified that there is service code assigned for "Barge in to another extension's call": (0511 item 61 is set to "810")

I've enabled "barge-in initiate" and "barge-in" receive for class of service 1, and verified that the ports are assigned to class of service 1 for day and night mode. (0406 items 65 and 66 are both set to "1")

Every time I try to use the feature, by dialing 810 followed by an extension, I get the fast high-pitched two-tone error. I get the same behavior if I set a "programmable function key" to "Barge In" code 1019.

I tried both enabling and disabling "Barge-in with Transmitter off" in program 0406 item 44, but it did not make a difference.

I also made sure there we values set for "Barge-In, intrusion tone" (program 0108 item 41), but I have not modified them. The current values are "001 1 19 005 36" for unit 1, and "00 000 00" for units 2-8. I can't imagine this would make a difference though.

We are not using the "ACD" feature.

I did not try re-starting the switch after I made the configuration changes, since I've found most class of service changes take effect immediately.

What am I missing?

System: NEC/Nitsuko 124i, software v6.00.15, standard CPU

Thank you
Eric