Something I tried unsuccessfully to sell at Teletype was that every selector magnet should have a

low voltage transistor selector magnet driver with an input level something like RS-232, operated by

voltage rather than current.  Something I later did with some of my own machines was to have a

120V 60ma selector magnet driver on every selector magnet and again with some kind of voltage

rather than current input to the SMD.  At one time this was grid voltage for a vacuum tube SMD,

and later something like RS-232 with a transistor driver.  Doing this for myself turned out to be more

work than I was willing to put into it.

 

Jim W6JVE