What is this block?

Hi, does anyone know what this block is?

Answer 1

[kei hin]

Sign->Indicate sign of input.

• The output is 1 when the input is greater than zero.
• The output is 0 when the input is equal to zero.
• The output is -1 when the input is less than zero.

http://www.mathworks.com/help/simulink/slref/sign.html

Your block is reversed. You can press the right key on it to see the help.