German air-warning system

"German Air-Raid Warning System" from Tactical and Technical Trends

The following intelligence report on the German WWII air defense system appeared in Tactical and Technical Trends, No. 21, March 25, 1943.

[DISCLAIMER: The following text is taken from the U.S. War Department publication Tactical and Technical Trends. As with all wartime intelligence information, data may be incomplete or inaccurate. No attempt has been made to update or correct the text. Any views or opinions expressed do not necessarily represent those of the website.]

GERMAN AIR-RAID WARNING SYSTEM

Recent reports from German sources indicate that all of Germany and German-occupied countries are divided into air districts numbered I, II, III, etc. Listening devices on the coast or frontier detect the approach of enemy planes while they are still at a considerable distance from any German air district. These listening devices, it is said, can detect the motor noise of an enemy plane as far away as 175 miles. When the sound of the motor is picked up, those districts toward which the planes are flying are alerted first. In this preliminary alarm, all factory lights which are noticeable are extinguished, radio stations go off the air, and the crews of antiaircraft guns prepare for action.

As the planes approach the coast or frontier, it becomes evident toward which district the planes are flying. That district is then put in the second state of alarm, which means that the sirens are sounded and everybody goes to the air-raid shelters. All factory lights--including emergency lights--are extinguished, and everything is put into readiness by the antiaircraft crews.

In the case of a typical example, it may be assumed that hostile planes are approaching air district I (see accompanying map), which is then put in the second state of alarm, while all districts bordering on No. I (districts II, VII, and VIII) are automatically put in the first state of alarm.

As soon as the attacking planes enter district I, it is put in the third state of alarm (Hoechstalarm, or maximum alarm), meaning "the enemy is attacking." The antiaircraft guns begin to fire and pursuit planes take off.

At the same time, the bordering districts II, VII and VIII are automatically put in the second state of alarm, and all districts bordering these (in this case, IX, X, XII, and III) are automatically put in the first state of alarm.

If the attackers fly on toward the district II, that district is put in the third state of alarm. As soon as the planes cross its border, all bordering districts, including district I, are automatically put in the second state of alarm. If the planes continue further inland, e.g., toward Berlin, all the districts in the line of flight, and over which the planes have passed, remain in the first state of alarm until the planes have entirely left Germany and German-occupied territory, and the attack can be considered terminated.

A German RRH acoustic locator 1940s

This apparatus was called the Ringtrichterrichtungshoerer (RRH). This ‘ring-horn acoustic direction detector’ was mainly used in World War 2 antiaircraft searchlight batteries for initial aiming of the searchlights at night targets, presumably because it was cheaper and easier to make than a radar set. Later in the war they were replaced by radar sets. Like the British and French versions, the RRH was also composed of four horns, two to determine bearing, and two for elevation, arranged in a ring. The two lateral horns have a horizontal bar across their mouths.

source: http://www.lonesentry.com/articles/ttt07/air-raid-warning-system.html