The answer to Max Lazarus' question regarding the disappearance of the trolley bus (Letters, 12 February) is, as always, economics.
When introduced, each trolley bus company generated its own electricity, so that the bus going downhill or stopping, put regenerative power back into its own grid, which reduced the power requirement from the generating plant.
With the switch to a national grid and the difficulty of measuring and reimbursing users for power they supplied locally back into the grid, the costs just did not work out.
With readily available electronic metering that meters power consumed and supplied — and hopefully a more open system of billing that reimburses users supplying back into the grid, as is required for all the green intiatives that encourage small-user solar or wind generation — their comeback could now be a reality.
Jim Edwards
Selsey, West Sussex
Back in the trolley

Radio wave weapon knocks out drone swarms
Probably. A radio-controlled drone cannot be completely shielded to RF, else you´d lose the ability to control it. The fibre optical cable removes...