Compendium 3 and 4 contains a facsimile reprint of the German World War 2 publication entitled ‘Signal Equipment’ (‘Nachrichtengerät’), also known as D50/13. The publication is Volume 13 in the ‘Foreign Equipment Data Sheets’ (‘Kennblätter fremden Geräts’), a series of German Army publications providing data on enemy equipment, principally from Belgium, England, France, North America, Russia and Switzerland. It was first issued to the German forces in July 1940, completely revised in 1941, with supplements issued in 1941, 1942 and 1943. For practical reasons the reprint was split into two parts: Compendium 3 covering the Belgian, English, French and North American sections containing 225 different signal instruments in 474 pages, and Compendium 4 with the Russian and Swiss sections, containing 171 different signal instruments in 364 pages. For English-speaking readers an English introduction, table of contents, glossary and translation of original German sample pages are provided. The facsimile reprint represents the D50/13 publication as it was used issued and updated, including all supplements, of which the last was issued in November 1943. ‘Foreign Equipment Data Sheets’ is a series of 15 different German Army publications providing principal data on enemy equipment ranging from small arms, heavy weapons, ammunition and vehicles, to communication equipment. They were compiled by the German high command, based on captured equipment and handbooks, but also from various (commercial) documents and journals, and issued to the German Forces as a guide to the reuse of the equipment. The publications are loose leaf allowing the replacement of obsolete and incorrect pages, and the addition of new pages in order to keep up with developments. Original and complete copies are rare.