- Electrical characteristics (AC or DC, Voltage...) of the installation for which the CB is intended.
- Its environment: ambient temperature, in a kiosk or switchboard enclosure, climatic conditions, etc.
- Presumed short-circuit current at the point of installation.
- Characteristics of the protected cables, busbars, busbar trunking system and application (distribution, motor...)
- Co-ordination with upstream and/or downstream device: Discrimination (selectivity), cascading, coordination with switch disconnector, contactor.
- Operational specifications: requirements (or not) for remote control and indication and related auxiliary contacts, auxiliary tripping coils, connection.