Document the invalid range for the logic levels for the multiplexer.

LED1 VCC 5.0V LED2 R1 U2A CLA1 U3 100 100 U1 5Hz 74LS393N 1Y 1c1 LED3 2 202 203 LED4 208 20C 20p U4 -2C 8Hz 74LS393N 74LS153N S1 GND Key A U5A S2 -1PR 10 ?? 15Hz icia 1K -10 Key S -1CLR GND 74LS76N LED1 VCC 5.0V LED2 R1 U2A CLA1 U3 100 100 U1 5Hz 74LS393N 1Y 1c1 LED3 2 202 203 LED4 208 20C 20p U4 -2C 8Hz 74LS393N 74LS153N S1 GND Key A U5A S2 -1PR 10 ?? 15Hz icia 1K -10 Key S -1CLR GND 74LS76N