Philips DVDR985 Technical Training Manual page 45

IR Receiver
The IR receiver, 7140, contains a bandpass
amplifier as well as a photo-diode. Refer to
Figure 19. The photo-diode receives approxi-
mately 940nm infrared pulses. The pulses are
amplified and demodulated. On the output of the
IR receiver, 7140, is a pulse sequence at TTL
levels. The IR signal appears on Pin 5 of 1917
on the Front Panel. The IR signal goes to Pins
12 and 13 of 7160. 7160 establishes a minimum
threshold for the IR signal to trigger its gate. This
filters out erroneous IR from reaching the
Microcomputer.
The RC connection on the rear of the unit comes
through the Analog PCB to 1916 Pin 10. This
signal also goes to 7160, Pin 5. This pulse
sequence is an input to the controller for further
signal evaluation via IRR input on 7156, pin 2.
Bi-Color LED (Standby and ON)
The STBY-LED is a red/green bi-color-LED con-
trolled by the STBYLED signal on Pin 10 of
Figure 19 – IR and Standby Panel
7156. The LED drive circuit receives the 5Vdc
Standby supply. The control voltage coming from
the Microcomputer is inverted by 7164. When
the LED control voltage on the microcomputer is
High, a Low goes to the LED drive circuit, turn-
ing the LED green.
Figure 20 - Basic Engine (BE)
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