The Maximum Length and Isomorphism of Circuit Codes with Long Bit Runs

Recently, Byrnes presented a formula for the maximum length of a symmetric circuit code that has a long bit run and odd spread. Here we show that the formula is also valid when the spread is even. We also establish that all maximum length symmetric circuit codes with long bit runs are isomorphic for an infinite and nontrivial family of circuit codes, extending a previous result of Douglas.