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EMD F7 B

The F7 was the fourth model in GM-EMD's successful line of F-unit locomotives and by far the best-selling cab unit of all time. In fact, more F7s were built than all other F units combined. The F7 succeeded the F3 model in GM-EMD's F-unit series, and was in turn succeeded by the F9. Final assembly took place at the GM-EMD plant in La Grange, Illinois, or at the GMD plant in London, Ontario. There was no F4, -5 or -6 model; "7" was chosen to match the contemporary twin-engine E7, and was also applied to the new GP7 road switch.

The F7 differed from the F3 mainly in its internal equipment - mainly electrical - and some external features. Its continuous tractive effort rating was 20% higher, for example 40,000 lbf (180 kN) for an F7 with a 65 mph (105 km/h) gear, versus 32,500 lbf (145 kN) for an F3 with the same report.

A total of 2,393 cab-equipped A main units and 1,463 cordless or B main units were built. [1]

Many F7s remained in service for decades, as railroads found them economical to operate and maintain. However, the locomotive was not very popular with the yard crews who used them in switching duty because they were difficult to assemble and disassemble, and it was also nearly impossible for the engineer to see the hand signals of a ground crew without leaning out of the window. As most of these engines were purchased and operated before two-way radio became standard on most American railroads, this was a major point of contention. Later, with the advent of "route switchers" such as the EMD GP7, F units were primarily used in "direct freight" and "unit train" services where there was little or no switching at carry out.
https://en.wikipedia.org/wiki/EMD_F7

LOCAL CONTROL MUST BE ENABLED TO CONTROL MOTOR