Detect infrared codes from the remote controller

I have in my home an air conditioner and his remote controller that control by IR communication so when I touch one command in the remote controller the led of the remote controller become to flick in one frequency for example 100 flickers per second and this say for example to the air conditioner to up the temperature by 1 degree of celsius and if I touch other button for example to change to cold mode so the led flick in other frequency for example 500 flickers per second, I have the air conditioner remote controller (the sender), the air conditioner (the receiver) and universal remote controller for air conditioners but I don't know the codes )the frequencies of the led for every command) so I want to find it or to discover it so my question is how I can do it?
Is exist one device that can detect the codes of the remote controller? if yes so I will glad if you can add a website about this