The Michigan Emergency Public Safety System (MEPSS), operates in simplex mode on 155.865 MHz. This is a statewide mutual aid/coordination frequency, used by all public safety first responders across the state. I believe that this is F-4 is most radios in Gratiot County. However, that may have changed that since they purchased new high-capacity two-way mobile and portable radios a few years ago.
Actually the call tone is CTCSS 123 I believe. I have not programmed the call tone since other departments may have a different tone and I just have MEPSS in my statewide list. Gratiot uses MEPSS on a not quite daily basis. It is used as a semi-private channel because I think they think a lot of people do not monitor it.