I'm not well versed in the entire (phone) network space. Ericson switch uptime (powered by Erlang) is always cited and admittedly initially drew me to the whole

I'm not well versed in the entire (phone) network space. Ericson switch uptime (powered by Erlang) is always cited and admittedly initially drew me to the whole ecosystem. Well mostly the "it's used in a network that has basically worked all these years so it must be rather robust one way or another" line of thinking. However what I'm wondering is...there's other vendors and Ericson isn't powering the entire network. What software stacks are used by other vendors? I'm assuming it's mostly C-ish stuff with some ASM sprinkles like in Cisco IOS?