Tom, Ray has passed along some highlights -- I'd just add some thoughts of my own: (1) Lee made have had reference to plaintext transmissions. Based on grade and status as brigade cdr, Imboden may not have been issued official CSA cipher, nor had provision been made for an acceptable substitute. (2) While Ray has covered the mil wire-tapping aspect, there was an additional concern that plagued the security-minded: newsmen loitering around the tel office, hoping to pick up a "scoop" by "ear," i.e., evesdropping on the tel op or his instrument's click. (One of Major Norris's final actions was a change of key and operational procedures to counter just such a situation in a Georgia tel office.)|
While (as Plum notes) many of the commercial tel ops in the pre-war South were Northerners (or Canadians), they seem generally to have adhered to their required oath of confidentiality and conducted themselves in an apolitical manner. As I'm entering the discussion late, I'd stress the caution against plain language revelation as Lee's May 1863 concern, and that concern based upon direct or indirect knowledge acquired by "the media" and revealed in the press.