ORIGINAL: ausf
I did crack the top off the $11 HL apple (It'll be obsolete to me as soon as the DBU arrives) and it's only 1 sensor with a chromed plastic pyramid to deflect the signal. Pretty cheesy, but it works (kind of sums up HL, huh?)
The Tamiya TBU looks very much like the HL. The chrome pyramid is a better quality chrome plating. Heng Long pretty much copied the TBU, but left the LED's out.. The 45 degree defense is because of that pyramid, When the leading edge of that pyramid faces the IR shot, it is not deflected down on to the sensor.