CIRCUIT DESCRIPTION
TUNING VOLTAGE GENERATOR
BT BS TU H/L 1 16 BU
VREF Vcc
VCC6
IC500 MSC1169MS-K GND U/V 8 9 VH2 H/L R502 R501 R500 6 11 VH1 TU 7 10 VL1 IN 4 13 VL2 OUT 5 12 U1 BS 2 15
3 14 U2 BT
VREF
GND Figure 1 This circuit generates the DC tuning voltage BT for selecting a channel with a TU pulse being output from IC700. IC500 has 3 circuits for converting pulses to voltages; it selects one of VHF-L, VHF-H, or UHF, and causes the tuning voltage to be output from the OUT terminal (pin 12). Figure 2 and Table 1 show the conditions for selection. IC500 Inputs
VHF -L 11 VHF -H 12
Function U/V L L H H H/L L H L H VHF-L receiving VHF-H receiving UHF receiving UHF receiving
