A signal elbow is a conduit with signal output 90 degrees from its input. This term is commonly used only for signal wires, particularly 2c/3 signals. A Snark could reasonably be called a "glider elbow", but "glider reflector" is the standard term. A signal elbow with a recovery time less than 20 ticks would enable a trivial proof that Conway's Life is omniperiodic.
A near miss is the following elbow-like converter found by Dean Hickerson. It successfully turns a 2c/3 signal by 90 degrees, but unfortunately changes it to a double-length signal in the process. This means that further copies of the converter can not be appended (e.g., to make a closed loop).
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RLE: here Plaintext: here
Relatively small composite MWSS elbows can now be constructed, using Tanner Jacobi's 2015 discovery of a small H-to-MWSS component. For example, the Orthogonoid includes a constructor/reflector that reflects an MWSS stream by 180 degrees, but it can be trivially reconfigured to make a 90-degree MWSS elbow.