On the original 'Dragnet' Ben Alexander played Jack Webb's partner. What was his character name?

Officer Frank Smith was the character name.

However, this was originally played by Herbert Ellis for 8 episodes before Ben Alexander made his first appearance as the character. Herbert Ellis made a further appearance as Frank Smith before Ben Alexander took over the role permanently.

https://en.wikipedia.org/wiki/Herb_Ellis_(actor)

https://www.imdb.com/name/nm0018273/

Dragnet had its beginning on the radio. The first Dragnet show aired on June 3, 1949 on NBC Radio. And, like the television shows and movies that followed, Dragnet on radio stared Jack Webb as Sergeant Joe Friday. Even after Dragnet made its televison debut in December 1951, the show remained so popular that the radio broadcast continued through 1957.
During the run of the Dragnet on Radio, Sergeant Joe Friday had a variety of partners. His first partner was Ben Romero played by Barton Yarborough. After Yarborough's death in 1951, Friday's received a new partner, Ed Jacobs, played by Barney Phillips. After Jacobs, Friday's was partnered with Officer Frank Smith who was played by a string of actors including Harry Bartell, Herb Ellis, Vic Perrin and Ben Alexander
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