Emission category
The more powerful the transmitter in your cellphone, the better it will be in giving you coverage in remote areas. Hand portable phones are Class 4 devices (as defined by the DTI) and offer maximum output of 2 Watts (although this is usually limited to 0.6 Watts). Carphones and transportables are usually Class 2 devices offering a maximum signal output of 8 Watts.

ESN
Each cellular phone is assigned a unique ESN, which is automatically transmitted to the cellular tower station every time a cellular call is placed.

ETACS
Extended Total Access Communications System. The standard used by UK analogue cellphones. Originally termed TACS, additional frequencies were added to increase network capacity.

ETSI
European Telecommunications Standards Institute. The people who wrote the specification for GSM and DECT.