A look at RCBOs and how they are fitted into a typical consumer unit.
RCBOs are a single device which combines a circuit breaker and RCD.
As they must sense the current in both the line and neutral, they have connections for both.
This example has a flying lead for the incoming neutral connection and a standard terminal for the line busbar. A smaller white lead is a functional earth connection.
Outputs are via two terminals on the top of the device.
Although more expensive than a consumer unit with one or two RCDs and separate circuit breakers, RCBOs have the advantage that a fault will only affect a single circuit.