Erlang is a programming language originally developed at the Ericsson Computer Science Laboratory. OTP (Open Telecom Platform) is a collection of middleware and libraries in Erlang.
Erlang/OTP has been battle tested in a number of Ericsson products for building robust fault-tolerant distributed applications, for example AXD301 (ATM switch).
Main developer and maintainer is the Erlang/OTP unit at Ericsson.
Source: About - Erlang/OTP