French high level code

In my post on the Battle of France there was mention of a high level code used between the War Ministry and the Army Groups.In ‘’Decrypted Secrets’’ it’s called  a ‘’transposition for superencryption’’.

I found more info on this code in Ticom I-128 and I-58.

According to I-128 ‘’Deciphering Achievements of In 7 /VI and OKW/Chi’’  the network radiating from Paris was called FLD by the Germans.I don’t know if the code had the same designation.

I-58  ‘’Interrogation of Otto Buggisch of OKW/Chi ‘’ p2 mentions a French diagonal write-out transposition.I assume that it’s the system mentioned by Bauer in ‘’Decrypted Secrets’’.