Well it was natural for LRH, a "nuclear physicist," to think in those termsI'm sorry to labour the point, perhaps I'm just bored this evening, but in the 50's most adding machines were mechanical and not electrical. The 'held down 7's' made perfect sense to me at the time though.
Railways run on electricity with lines and terminals but they have nothing to do with the mind.
I saw a 1920s Burroughs mechanical adding machine a few years ago, in a college professor's office. Burroughs as in William Burroughs, the Scientologist/Beat writer. The same company, through various mergers, was responsible for the famous Univac computer Hubbard would have known about back then.