The best example of this is the old "all American five" tube radio where they had tube filaments ranging from 12v to 50v and they all used 150MA but the effective resistance was selected so they could take 120v line power in series to light them all up.
That was common in Britsh radio and TV equipment of the era too, although with supplies of 200 to 250V the typical table radio with five tubes had to employ a series dropper resistor as well.
In fact the Mullard valve coding system used by tube manufacturers here had the first letter denote the heater characteristics, and some were specifically reserved to designate tubes intended for series connection: P was 300mA, U was 100mA, and so on, the latter being very common on domestic radios of the era (UCH81 converter, UL84 output pentode, etc.).
During the immediate post-war period we imported quite a number of those "All American Five" designs too, modified for U.K. use. One method of adapting the series filament chain for 200-250V was to use a very long power cord which had a nichrome resistance element as one conductor to act as the extra series resistance.
Apparently it worked quite effectively -- Until somebody decided that he didn't like the 9 or 10 ft. cord and tried to shorten it.
