In diameter, to a total resistance of zoo ohms. The actual current required to work the instrument is 3.3 **milliamperes** (equivalent approximately to the current given by 1 Daniell cell through 3300 ohms), but in practice a current of to **milliamperes** is allowed.

40 ohms (or 900 ohms when worked from accumulators), and the instrument is worked with a current of 400 **milliamperes** (25 milli British Post Office.

The standard relay will work single current with a current of 3 **milliamperes**, though in practice about 10 would be used.