Blue Lava,
1. What you say is absolutely wrong. Welltech support only hardware answer/disconnect supervision on analog lines, based on line polarity reversal detection.
They ***DO NOT*** support voice based answer/disconnect supervision.
Instead of leading VoIp training at your company, you should take such one by yourself.
2. Even if Welltech have had voice based answer/disconnect supervision, buying it from you will be the last thing I am going to do on this Earth. I have learned my bitter lesson already by sending you money for a set of Quintum gateways.
I am Teodor Georgiev from VoiceLink Communications, Bulgaria. Do you remember me?