Guardkore Push to talk GSM PTT Radios is a state-of-the-art Push to talk (PTT), Smart-PTT, GSM Radios service based on Cellular Networks. Radios rely on GSM, 2G Radio, 3G radio, 4G radios, LTE Radios signal. Our radios will be able to talk to each other without any range restriction, as long there is network coverage. Each Two way Radio works with a SIM card and uses GSM 2G/3G/4G and some models even work with a WiFi signal. This means that our clients don’t need to spend a fortune on expensive radio infra-structures, like repeaters, antennas, or leasing sites.