A rare form of " C " battery was the " bias cell ", a button-size miniature battery designed to deliver a constant voltage with no current drain.
12.
It is usual for such systems to include a backup battery, either disposable in a holder ( current drain is extremely low and life is long ) or soldered-in rechargeable.
13.
Button cells have a limited current drain; for example an IEC PR44 cell has a capacity of 600 milliamp-hours ( mAh ) but a maximum current of only 22 milliamps ( mA ).
14.
These are most commonly used in portable devices that have low current drain, are used only intermittently, or are used well away from an alternative power source, such as in alarm and communication circuits where other electric power is only intermittently available.
15.
:If you make logic gates out of transistors without matching all the impedances and current drains for the entire analog states encountered in operation, something with 5 gates might work fine, but extending it to 6 gates might suddenly fail with no obvious reason.
16.
Generally ( but not always ), user-accessible ports on a computer are pretty well protected against excessive current drain, short circuits, improperly applied power and other common problems, simply to avoid accidental damage to internal components due to a failure in a peripheral . ( I know this from working with this sort of protection circuitry . ) talk ) 16 : 41, 14 December 2012 ( UTC)
