List of electrical characteristics of single collision domain segment "slow speed" network buses:
The number of nodes can be limited by either number of available addresses or bus capacitance. None of the above use any analog domain modulation techniques like MLT-3 encoding, PAM-5 etc.
PSI5 designed with automation applications in mind is a bit unusual in that it uses Manchester code.
References
List of network buses Wikipedia(Text) CC BY-SA