What would be the circuit equivalent be of a uniselector, aka rotary relay, aka stepping relay?
Uniselectors were commonly used for phone switch boards (and thus why we used to hear individual pulses). The uniselector:
- has high-voltage galvanic isolation between inputs (easily hundreds if not thousands of volts)
- carries bi-directional, high current at low resistance
- incrementally steps between inputs, guaranteeing input pairs stay exclusive
- has a floating ground (it really has no ground at all)
An array of bistable relays, controlled by a decade counter and an overlap protection circuit, is the closest I can come up with. However, this feels very unsatisfactory as its needlessly complex in part count.
Transistors and FETs do not provide isolation, so are not a replacement.
Analog switches are not an equivalent as they have relatively high internal impedance (>1ohm), and thus cannot carry much more than signal current.