A system comprising: a first filter configured to: receive modulated electricity having at least two different alternating current frequencies over an electrical line, the at least two different alternating current frequencies including a first alternating current frequency and a second alternating current frequency, and attenuate the second alternating current frequency of the modulated electricity to obtain filtered modulated electricity that is predominantly of the first alternating current frequency; and a computing device powered by the filtered modulated electricity; characterised in further comprising: a second filter configured to: receive the modulated electricity having the at least two different alternating current frequencies over the electrical line, and attenuate the first alternating current frequency of the modulated electricity to obtain second filtered modulated electricity that is predominantly of the second alternating current frequency; and a second computing device powered by the second filtered modulated electricity. a first filter configured to: receive modulated electricity having at least two different alternating current frequencies over an electrical line, the at least two different alternating current frequencies including a first alternating current frequency and a second alternating current frequency, and attenuate the second alternating current frequency of the modulated electricity to obtain filtered modulated electricity that is predominantly of the first alternating current frequency; and a computing device powered by the filtered modulated electricity; characterised in further comprising: a second filter configured to: receive the modulated electricity having the at least two different alternating current frequencies over the electrical line, and attenuate the first alternating current frequency of the modulated electricity to obtain second filtered modulated electricity that is predominantly of the second alternating current frequency; and receive modulated electricity having at least two different alternating current frequencies over an electrical line, the at least two different alternating current frequencies including a first alternating current frequency and a second alternating current frequency, and attenuate the second alternating current frequency of the modulated electricity to obtain filtered modulated electricity that is predominantly of the first alternating current frequency; and a computing device powered by the filtered modulated electricity; characterised in further comprising: a second filter configured to: receive the modulated electricity having the at least two different alternating current frequencies over the electrical line, and attenuate the first alternating current frequency of the modulated electricity to obtain second filtered modulated electricity that is predominantly of the second alternating current frequency; and a second filter configured to: receive the modulated electricity having the at least two different alternating current frequencies over the electrical line, and attenuate the first alternating current frequency of the modulated electricity to obtain second filtered modulated electricity that is predominantly of the second alternating current frequency; and receive the modulated electricity having the at least two different alternating current frequencies over the electrical line, and attenuate the first alternating current frequency of the modulated electricity to obtain second filtered modulated electricity that is predominantly of the second alternating current frequency; and a second computing device powered by the second filtered modulated electricity.