It is basically a trunked radio system based on GSM. you can simply say trunked GSM. It is suitable for land based trunked radio. It has for distinct band i.e.
T-GSM 380 band:
- 380,2 MHz to 389,8 MHz: mobile transmit, base receive;
- 390,2 MHz to 399,8 MHz base transmit, mobile receive.
T-GSM 410 band:
- 410,2 MHz to 419,8 MHz: mobile transmit, base receive;
- 420,2 MHz to 429,8 MHz base transmit, mobile receive.
T-GSM 810 Band:
- 806 MHz to 821 MHz: mobile transmit, base receive;
- 851 MHz to 866 MHz: base transmit, mobile receive.
T-GSM 900 Band;
870.4 MHz to 876 MHz: mobile transmit, base receive;
- 915.4 MHz to 921 MHz: base transmit, mobile receive.
For more detail you can google it. there is lot of information about it.