Telnet - Client - get talking user doesn't work

Hello,

here is the situation:

I connect to the client via telnet, receive the clients with their ids located in my channel, then i wanna know who is speaking.

Here starts the trouble:

i call:
clientvariable clid=CLIENT_ID client_is_talker client_nickname

result:
client_is_talker is always 0,

how can i get the people actually talking right now? am i missing something?

Thanks four your help : )

Telnet - Client - get talking user doesn't work