Back 37 APPENDIX B Cross Reference Chart Discontinued Headset   Model Numbers Old Group Codes Equivalent New Technology (M10) Switch Settings MHB224-1 2 M1 MHB424-1 MHB524-1 MHB525-1 MHB524-1NC MHB525-1NC MHB228-3 MHB224-1 M2 MHB428-3 MHB528-3 MHB529-3 MHB528-3NC MHB529-3NC MHB230-1 3, 10 M5 MHB430-1 MHB530-1 MHB531-1 MHB530-1NC MHB531-1NC MHB228-1 5 M5 MHB428-1 MHB528-1 MHB529-1 MHB528-1NC MHB529-1NC MHB228-2 11 M5 MHB428-2 MHB528-2 MHB529-2 MHB528-2NC MHB529-2NC