RCD Safety Switches are required by law to be fitted at the origin of the power and lighting circuits which will be at the main meter box or distribution board for the residence. They can be identified by the test button on the front of the device.
Since 2000 it has been compulsory for all new homes to have a minimum of two RCD Safety Switches fitted to protect the power and lighting circuits as part of the electrical installation. However,
homes built before 2000 were not required to have two RCDs fitted and from 1992 to 1999 only one RCD was fitted, which will not ensure complete protection for your family.
One RCD is likely to protect only the power circuits and leaves the lighting circuits unprotected.