There are some contests such as ARRL's Field Day that provide special categories or points for contestants who operate using emergency or battery power. The 2016 FD rules for "Class A - Battery" stations include this text:
All contacts must be made using an output power of 5 Watts or less and the power source must be something other than commercial power mains or motor-driven generator (e.g.: batteries, solar cells, water-driven generator).
The same text is included for "Class B - Battery" stations. The text for "Class E" stations is different:
Same as Class D, but using emergency power for transmitters and receivers.
On first glance, this would imply that "Class E" stations -- but not "Class A - Battery" or "Class B - Battery" -- can use commercially-powered equipment such as computers for logging or digital modes such as PSK31, as long as all transmitters and receivers are using emergency power. Is this an appropriate interpretation of the rules?