1. Your PBX does not support mulipart calls. Contact your PBX reseller for upgrading.
2. Your PBX needs another command than R3 to connect more parties, read the table below.
Note that the commands can differ due to settings in the PBX.
| Brand | Model | Command | Notes |
| Aastra | BusinessPhone | F3 | |
| Avaya | IP Office | *47 | |
| Avaya | Integral 55 | F4 | Add-on conference must be active |
| Ericsson | MD110 | 3 | |
| Euro | Generis | F63 | |
| Philips | Sopho IS3000 | F | F*3 for new line |
| Samsung | Office Serv 500 | 46 | |
| Unify/Siemens | HiCom Office | *5 | |
| Unify/Siemens | HiPath | *3 | or F*3 or *53 |
| Vox | Novo | F4 | |
| NEC | SV8100/9100 | Instructions |