Ternary Hardware – CMOS switches
Here I use undocumented feature of DG403 when normally closed switch opened by voltage lower than required to close another (normally opened) switch. Variable resistor is used to move that “both-opened” window to ternary “0″ zone (up from -3.0V…-0.8V to cover 0V).
Second scheme is more “correct” (nothing from undocumented features were used).
P.S. Ternary selector may be used as ternary inverter when RP=-5V, RO=0V, RN=+5V. See more details on www.ternary.info