I have a use-case where I need to control 4+ sonar sensors with a pic 628A microcontroller. The pic is also responsible for controlling a GPS and LCD so pins are scarce. The sonar sensors each have a single signal pin. To operate them, you pulse this pin which produces an ultrasonic chirp and then wait for it to go high again which indicates that an echo was detected. The time between the initial pulse and the response pulse corresponds to the time of flight of the chirp.
I would like to be able to multiplex all of the sonar sensors onto a single bus, but am not sure how to accomplish this. I would like to use only basic components if possible (not specialized IC's) because my main purpose of this experiment is to get a better understanding of the basics. Since the signal channel must allow for both input and output, I do not think bipolar transistors will work. I have considered using FET's to multiplex each signal line, but I am very inexperience with this stuff and would appreciate some direction.