The BTS (Base Transceiver Station) provides two-way radio communication between mobile stations and the PSTN (Public Switched Telephone Network) within a single GSM cell. It has four primary functions: transmission, telecommunication, operation and maintenance (O&M), and support. The transmission function manages the transfer of traffic and control data between the BTS and BSC (Base Station Controller) via the Abis interface. The telecommunication function modulates signals for transmission and demodulates received signals. The O&M function monitors and controls the BTS. The support function provides internal power, temperature control, and other services.