Meridian Laboratory - ROTOCON Brushless Slip Rings often outlast conventional brushed slip rings between 5 & 25x without the need for maintenance, adjustment, or downtime. . . https://www.meridianlab.com/products/rotocon-m-multi-channel-end-shaft-slip ...
ROTOCON M | End-of-Shaft Slip Ring Alternatives (4 Contacts)
Standard versus custom slip rings — and inductive, capacitive, wetted mercury variations
What are some alternatives to slip rings? - Quora
Types and Usage of the Slip Rings - The Engineering Projects
Slip ring substitute promises no wear for life of turbine