two consecutive timeslots serve one TCH only. So in your example :
TRX 1 = 6 radio TS = 3 TCH
TRX 2 = 8 radio TS = 4 TCH
But this is a extended cell as implemented by ericsson or huawei. For alcatel, for example, the extended cell uses a different solution. The max range = 64km only, but 1 radio TS = 1 TCH.
Regards,
Pix