An interlocked circuit breaker system: a first circuit breaker, wherein the first circuit breaker includes a first external mechanism, a first shaft assembly and a first contact mechanism coupled to the first shaft assembly; a second circuit breaker, wherein the second circuit breaker includes a second external mechanism, a second shaft assembly and a second contact mechanism coupled to the second shaft assembly; a first linkage coupled directly between the first shaft assembly and the second contact mechanism; and a second linkage coupled directly between the second shaft assembly and the first contact mechanism wherein: if the first circuit breaker is in a closed position, the second contact mechanism is disabled, and/or if the second circuit breaker is in a closed position, the first contact mechanism is disabled, wherein the first external mechanism manipulates the first contact mechanism, and the second external mechanism manipulates the second contact mechanism; the interlocked circuit breaker system includes a single module circuit breaker housing containing the first circuit breaker, the second circuit breaker, the first linkage, and the second linkage; and the first linkage is configured to mechanically disable the second contact mechanism, and/or the second linkage is configured to mechanically disable the first contact mechanism. a first circuit breaker, wherein the first circuit breaker includes a first external mechanism, a first shaft assembly and a first contact mechanism coupled to the first shaft assembly; a second circuit breaker, wherein the second circuit breaker includes a second external mechanism, a second shaft assembly and a second contact mechanism coupled to the second shaft assembly; a first linkage coupled directly between the first shaft assembly and the second contact mechanism; and a second linkage coupled directly between the second shaft assembly and the first contact mechanism wherein: if the first circuit breaker is in a closed position, the second contact mechanism is disabled, and/or if the second circuit breaker is in a closed position, the first contact mechanism is disabled, wherein the first external mechanism manipulates the first contact mechanism, and the second external mechanism manipulates the second contact mechanism; the interlocked circuit breaker system includes a single module circuit breaker housing containing the first circuit breaker, the second circuit breaker, the first linkage, and the second linkage; and the first linkage is configured to mechanically disable the second contact mechanism, and/or the second linkage is configured to mechanically disable the first contact mechanism. if the first circuit breaker is in a closed position, the second contact mechanism is disabled, and/or if the second circuit breaker is in a closed position, the first contact mechanism is disabled, wherein the first external mechanism manipulates the first contact mechanism, and the second external mechanism manipulates the second contact mechanism; the interlocked circuit breaker system includes a single module circuit breaker housing containing the first circuit breaker, the second circuit breaker, the first linkage, and the second linkage; and the first linkage is configured to mechanically disable the second contact mechanism, and/or the second linkage is configured to mechanically disable the first contact mechanism.