Hi guys,

Was look at a schematic earlier was confused on why the BJT was used in the following situation? The REC_OK is a signal sent from the DB-25 connector to the uP, which tells the uP that the DVR is recording fine.

 

The bjt amplifies and inverts the signal. The inversion might be important, and the amplification might not be important.

 

Thank you. Just read more about the common emitter amplifier. The spec sheet on the DVR doesn't give much information on it.

 

simple inverter - likely translates to the proper logic level as well - as was already suggested.