use of a gas,water or other service pipe as the main earth
It has never been permitted for gas pipes and has not been permitted for other service pipes since 1966.
voltage-operated earth leakage circuit breakers
two basic types of earth leakage circuit breakers used to be recognised by the wiring regulations: the current operated type (RCD) and the voltage operated type.
the voltage operated type ceased to be recognised in 1981.
absence of c.p.c. in lighting circuits.
All lighting circuits installed since 1966 ( with the exception of certain extra-low voltage circuits) have been required to include a c.p.c.
double-pole fusing
In many installations put in up to the 1950s, the circuits have a fuse in the neutral conductor as well as in the phase conductor. This is potentially dangerous for ac installations, and ceased to be permitted by the wiring regulations in about 1955.
non-13A socket outlets
the installation of socket outlets other than the current standard 13A square pinned type was common prior to the early 1950s. These outlets accept non-fused plugs( some with an earth pin and some without),generally having round pins.
concealed cables outside the safe zones
untill the latter part of the 1980s the wiring regulations did not contain any specific requirements for the positioning of cables concealed in walls or partitions.
Cables of imperial (non-metric) sizes
up until the beginning of the 1970s, cables could still be purchased having imperial, rather than metric, sized conductors.
Accessories on wooden mounting blocks
It was commonplace up to the mid- 1960s for accessories such as socket outlets light switches and ceiling roses to be fixed to wooden mounting blocks.