service_option field the mobile station shall set this field to a value less than or equal to max_num_alt_so s if the p_rev_in_use s is equal to or greater than 6 and the mobile station supports at leaset one alternate service option and max_num_alt_so s is greater than u2018 000 u2019 the mobile station shall set this field to the 3 lsb bits of the number of the so group defined in tsb58a containing the alternate service option supported by the mobile station otherwise the mobile station shall set this field to zero if this field is not zero the so group number is equal to the value u2018 1000 u2019 will not be used and u2018 1111 u2019 is reserved if mobile station shall set this field to the most singificant bit of the number of the so group containing alternative so supported by the mobile station for example if the so group number is 9 or greater this field is set to 1 if num_alt_so is equal to u2018 000 u2019 or p_rev_in_use s is less than 6 the mobile station shall omit this field otherwise the mobile station shall set each bit in the specified service option group that corresponds.