The BC548 family, including the BC547A to BC550C, are lower voltage, lower current, general-purpose transistors in TO-92 packages, originating in Europe, that are often found in small-signal amplification and switching circuits of the type where the 2N2222 might otherwise be used.
The BC548 family, comprising the BC547A to BC550C, are low-power, low-current transistors in TO-92 packages, originating from Europe, typically employed in small-signal amplification and switching circuits that could otherwise utilize the 2N2222.