I see these frequently on PCB figures (REF BSC TYP). Could someone kindly explain what these mean? REF = reference (to what)? I pretty sure that BSC is basic spacing between centers? TYP = ?
Also, in datasheet packaging sections, there is often a thin horizontal rectangle subdivided into (usually) 3 or 4 sections. Each rectangle usually starts w/ a symbol (for example, 1/2 circle or theta)in the first section, followed by sections w/ alphas or numberics - oftentimes accompanied by a letter in a circle. Could someone explain this or point me to an explanation as well?
Thanks, Tom