This longwave station has been developed by Telefunken, Deutsche Gesellschaft für drahtlose Telegraphie, Berlin. The first sets have been acquired in 1918/9 and the got the designation "Tragbar Schwere Funkenstation 18", it consisted of the valve transmitter AR 125 and a TRF receiver of an unknown type. After 1922, this early receiver has been replaced by the E 266, a TRF receiver with adjustable reaction.

After it's renewal, the station was renamed Tragbar Schwere Funkstation 25 / T.S.25: the transmitter was replaced by the higher power AR 245 and the receiver by the Spez 7Bs TRF receiver with two tuned circuits and a voice amplifier Spez 60 Bs, all made by Telefunken.

Transmitter Tfk AR 245	Receiver Tfk Spez 470 Bs

1926 the earlier transmitter AR 125 was replaced by the transmitter AR 245, with it's two more powerful triodes RS55, it had an antenna output power of 20 W, reportedly this was sufficient for distances up to 50 - 75 km.

The receiver Telefunken Spez 7 Bs from 1926 with two tuned circuits (two triodes RE062t) and a voice amplifier Spez 60 Bs has been replaced by the Telefunken longwave receiver Spez 470 Bs / E31 in the year 1932.

The Tragbar Schwere Funkstation 25 has been in use by the Signal Troops and in the Swiss Air Force, from 1919 - 1929 a total of 56 sets have been acquired. In 1947, the equipment was declared as war reserve and has been lquidated in 1956.