3.5L is for switching operation to LARC, on a machine already running v3.50.

Note:
The firmware for the Lexicon 300 effect processor was upgraded several times during production, finishing with version 3.5. 

This made the machine far more powerful and flexible, adding:
DUAL MACHINE functionality with several new audio configurations.
An extra LFO for modulation.
A version of the Lexicon 224XL Rich Plate algorithm.
Six new Split effect algorithms including chamber, delays, pitch shift and dither.
Several more small enhancements and fixes.


Unfortunately, Lexicon ran out of their v3.5 upgrade kits years ago, so many users have been stuck with v1.x or v2.x firmware. Just copying the ROMs is not enough - a custom GAL logic chip is required to complete the upgrade.
