Episode 6 - Swiss Trackman Fieldphone


This trackman railway instrument was made by Gfeller probably in 1963 (Date on capacitor). According to a label inside the instrument it was tested by Gfeller again in 1969, probably after inspection. The Swiss communications museum has the same instrument in it's collection and dates it to 1930. Probably possible, I rather think that's an error. My uneducated guess would be that a similar instrument in the 30ies would have used wood or leather as material. The innards and construction of my instrument is for sure more from the 50ies/60ies as the date on the capacitor (1963) and on the test label (1969) suggest. The date of 1986 on the RX/TX elements suggests that the instrument was in use probably up to the late 80ies/early 90ies. Update 20230423: Got two additional of these, both made in 1968, 1969 based on capacitor and testlabel date.

It can be transported rucksack style (It is heavy: 12kg!). According to the station signals noted in the instrument it was last used on the Sonceboz - Moutier Railway in the Swiss jura region. The different stations on the line and the portable instrument were called by signs based on different combinations of short and long rings.

The instrument has two railway telephone line type sockets and a matching patchcable packed. The case is made of metal and the body frame is made of light alloy. Appart from the standard fieldphone components like generator, ringer, coil, handset and battery it also features connections for an external signal-horn with additional external battery. The external signal-horn is activated by a dc relais which acts on the rectified ringing current on the line.

Unique feature

Backpack straps. Connections for an external signal-horn.




Back of the body, all parts but the ringer are mounted here. On the front panel, top row, the pins 1/2 on the left correspond to La and Lb and connect to the ringer and line sockets in the case. M/T are the handset connectors (Microphone and Telephone). On the right the hookswitch which switches both, the transmitter and receiver circuits. Below the hookswitch mechanism are the La and Lb sockets. On the right of it the battery door opening. Below that, hidden behind the capacitor and the rectifier, are the sockets for the external signal-horn and it's battery and the associated fuse. On the bottom panel mounted are the generator, coil and capacitor from the main instrument circuit. Additionally the rectifier and the relais for the external signal-horn. On the right the battery holder which holds a single 1,5V D-type element.

Inside of the case. On the right the connectors 1/2 corresponding to La and Lb to connect to the main body. In the middle the 2x 1750ohm ringer. On the right the two parallel line sockets.

The body mounted inside the case. Left of the hook the closed battery door. Below the hook mechanism are the La and Lb sockets. And below that the sockets for the external signal-horn and it's battery and the associated fuse. The ground socket is connected to the body.

With the handset on hook. This is a standard Swiss PTT type 1946 handset.

The TX and RX elements mounted are of standard Swiss PTT type 1946 size.

TX and RX elements back. The TX element is a Philips dynamic element for LB from 1986. The 95ohm RX element is from Gfeller, also with date 1986.

Inside the front door a box to transport the patchcord with special railways connectors is mounted.

The patchcable connected.

On top of the patchcable box the manually written indications of the station call codes. The stations are: Sonceboz, Bienne, Reuchenette, Tavannes, Reconvillier, Court, Moutier, Cortébert. I assume Poste S is the instrument itself.

Ready for transport.

Backpack straps. 12kg on the back!

Exploded. Disassembled for thorough cleaning when I first got it.

Electrical diagram (self made).

Update 20230423: Electrical diagram from another identical instrument (Made 1969, diagram glued into back of case).


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