In a small company, we have two networks with two different operators (with
following address ranges 192.168.1.x/24 so private and 192.169.2.x/24. you want to link the two networks on the same LAN with a single SSID
This is because the subnet mask! You use the networks 192.168.1.0/24 and 192.168.2.0/24. For two machines on each network can connect you need a mask of / 23 or 255.255.254.0! So that machines on the network know their field of communication goes from 192.168.1.1 to 192.168.2.254 192.168.1.0 which is the network address and 192.168.2.255 is the broadcast address.