What are the prerequisite conditions for a 'silent/electronic radar handoff' between adjacent radar control sectors without verbal voice coordination?

1. Both sectors share automated radar data processing systems, radar track identification is maintained, the aircraft is flying on an agreed route and altitude, and it crosses the sector boundary within published lateral and vertical LOA parameters.
2. Voice radios are completely broken in both facilities.
3. The aircraft is flying without a transponder.
4. The handoff is performed during an active thunderstorm.