https://iot-portal.com Development Blog — gsm intercom

  The raison d'etre of any voice intercom is, unsurprisingly, to make voice calls! It can have any number of fancy features and apps but without the ability to make calls it's useless. Unfortunately, the majority of intercoms on the market today have a real problem with this. 2G and 3G have a dedicated voice and SMS channels as part of the connection to the network which connect calls directly to the circuit switched analogue phone network. 4G has no native voice channel and does its calling through the internet in the same way as a VoIP call does and this...