IsbIt namespace std

I am reviewing some sample code that uses IsbIt. It compiles successfully on my machine.

The top of the code sample has "using namespace std;"

I try removing the namespace line and modifying IsbIt to read std::IsbIt and it doesn't work. Is IsbIt a subset of something?

there is no IsbIt or std::IsbIt in C++. Its probably either in a non standard header or maybe in the code itself.