A DATA STORAGE DEVICE

摘要

A memory (43) is arranged to store data such that each item of data has either a first or a second state. A power supply deriver (D1, D2) derives a power supply from a signal supplied to the data storage device. A data reader (44, 45) causes data to be supplied to a memory data output (43a) of the memory (43) in response to the derivation of a power supply. A switch (T) coupled to the data output (43a) is rendered conducting by data having the first state and non-conducting by data having the second state. An impedance (Z) is provided in the power supply path of the data storage device and the switch (T) is coupled in parallel with the impedance (Z) such that, in use, the impedance (Z) is short-circuited when the switch (T) is rendered conducting, whereby the signal supplied to the data storage device is modulated in accordance with data read out from the memory.