Basically used by a radio operator when a radio message would come in he would look at the clock and put the time on the message.
In 1934 the Reichheer contracted Junghans based in Schramberg to produce the first duty clocks for use in radio stations, they are known as “Betreibsuhren”, “Stationsuhren” or by current collectors as “Funkeruhren”. As the army grew, around 1937 two other manufacturers became involved in the production of Funkeruhren: Kienzle and Tobias Beaurle & Soehne, both based in Schwenningen. Funkeruhren were produced for the Heer, Luftwaffe and Kriegsmarine.
This mix of clients and manufacturers led to the existence of many different variations of the Funkeruhr.
More info here:
http://www.wehrmacht-awards.com/foru...d.php?t=368165
and here:
http://www.vintage-time.de/index.php...der-Luftwaffe/
Steve