The CalDigit Thunderbolt 3 devices, such as TS3 Plus, TS3, TS3 Lite, T4 Thunderbolt 3 RAID are backward compatible with legacy Thunderbolt 1 and 2 computers.
An adapter from Apple is required to convert from Thunderbolt 3 to Thunderbolt 2 protocols. A Thunderbolt 2 cable is also required in this setup.
This adapter will also enable your legacy Thunderbolt 1 and 2 computers to make use of many functions that Thunderbolt 3 has to offer including a dual extended monitor setup if it is supported by the computer’s GPU. The laptop charging feature however is not implemented in the legacy Thunderbolt computers.
Please notes that Apple’s Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter does NOT support bus powered Thunderbolt 3 devices directly, such as CalDigit Tuff X and Thunderbolt 3 mini Docks. All bus-powered Thunderbolt 3 devices should be connected to the Thunderbolt 3 computer directly or to a dual-port Thunderbolt 3 device such as TS3 Plus using Apple’s adapter to convert to the Thunderbolt 1 / Thunderbolt 2 computer.