Both cities you are asking about are broadcast via St. Louis County's 2nd Precinct on 155.565. Charlack units are referred to as 2Charles units and St. John units are referred to as 2John units. That frequency also includes county police units for the 2nd Precinct and several other munis, including Bel-Ridge, Bel-Nor, Hillsdale, Breckenridge Hills, Velda City, and Woodson Terrace.