Version 4
SHEET 1 880 680
WIRE -192 128 -272 128
WIRE 96 128 -192 128
WIRE 288 128 240 128
WIRE 496 128 432 128
WIRE 640 128 560 128
WIRE 496 160 464 160
WIRE -272 192 -272 128
WIRE 16 192 0 192
WIRE 96 192 16 192
WIRE 288 192 240 192
WIRE 464 208 464 160
WIRE 0 240 0 192
WIRE -272 336 -272 272
WIRE 0 336 0 320
FLAG -272 336 0
FLAG 0 336 0
FLAG -192 128 fm
FLAG 288 128 sin
FLAG 288 192 cos
FLAG 16 192 amp
FLAG 464 208 0
FLAG 432 128 sin
FLAG 640 128 r
IOPIN 640 128 Out
SYMBOL SpecialFunctions\\modulate2 96 128 R0
WINDOW 0 57 -14 Left 2
WINDOW 3 -1 130 Left 2
SYMATTR InstName A1
SYMATTR Value space=0 mark=100k
SYMBOL voltage 0 224 R0
SYMATTR InstName V1
SYMATTR Value 1
SYMBOL voltage -272 176 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V3
SYMATTR Value SINE(1 .5 4k)
SYMBOL Digital\\diffschmitt 496 80 R0
WINDOW 39 6 116 Left 2
SYMATTR InstName A2
SYMATTR SpiceLine Vhigh=5
SYMATTR SpiceLine2 Vt=0 tripdt=1n
TEXT -288 416 Left 2 !.options plotwinsize=0
TEXT -152 48 Left 2 ;freq = space + Vfm*(mark-space)
TEXT -288 464 Left 2 !.tran 0 500u 0 0.1u