German Field Telephone Equipment Reference
Feldfernsprecher 33 / Field Telephone 33
Description
The
feldfernsprecher 33 or FF33 is the standard German field radio of WWII. It is
a general purpose field telephone designed for wired communications. It was introduced
in 1933 as a modern replacement for the previous WWI legacy field telephones. It
can also be connected to the Torn. Fu. D2 and Torn. Fu. Bl, and F
series radio sets as a remote handset.
The phone case is 28 cm x21 cm x 10
cm and weighs 5.84 Kg. The phone is made
of the following components: a PTT (press to talk) handset, switchboard patch
cable, generator crank, shoulder strap, 1.5 volt battery and internal framework
for the telephone components. Accessories
available are: headphone (kopfhörer) and throat microphone
(kehlkopf). Used with the headset and throat microphone
was mainly for use by switchboard operators.
The set is housed in a bakelite plastic case which consists of two parts is
hinged and fastened with press to release spring latch. On the top of the upper
case are two white panels. The panel on the left is used to record information
such as call signs or station number while the panel on the right is inscribed
with the German phonetic alphabet.
A dust
cover on the front can be swung open to give access to two jacks; both jacks
are common and also common to the with the incoming line terminations on the
top of the phone. The jacks are used when patching two phones together or when
connecting a field phone to an exchange line via an exchange line adaptor. The
grill on the front of the case is designed to enhance sound of the ringer. On
the right side of the case is another access plate which protects the port for
installing the crank onto the generator. Sockets are located on each side of
the lower case along the edge for installing a carrying strap.
Looking
down into the phone you’ll see the following: The handset rests on top and when
the phone is open it is convenient to lay the handset in the open top. Inside
the top is a leaf spring that holds the handset in place when the phone is
closed[1]. The
battery compartment is on the end, covered with a hinged lid. Beside the
battery box is an open compartment where the patch cable and the handset cord
are stowed.
The handset
plugs into a center jack console with a unidirectional plug. Beside the plug
are two screw terminals marked Lb/E
and
On the right side of the panel the
white generator test button (Prüftaste).
Shorting the screw terminals and pressing the Prüftaste button while cranking
the generator will sound the local ringer as a test of the generator output.
The generator outputs of 84 volts AC as ringing current. Adjacent are the jacks
for headphones. The generator crank is stored in a hole and notch next to the
panel.
In the field, when set up for use,
the top cover is usually closed and the line and handset cord run out of the
unit by the end of the case near the battery box. A pair of soft rubber strips
built into the case cushions the cords when the lid is closed. The handset can
then be laid crosswise on the closed cover. The photo to the right shows the jäger talking
in the handset of a W28 telephone while the FF33 has its handset resting on the
top of the closed case. A special accessory is available that creates a resting
cradle for the handset on the closed lid. This was normally used with a
switchboard setup and not in the field.
The
telephone has two circuits, one is the ringing circuit
which temporarily connects the generator with the ringer via the telephone line
with ringing current. The other a talking circuit for communications is the
other and is powered by the local battery when the PTT in the handset is pressed.
When each station transmits, that only station’s battery is used, this
minimizes battery drain and maximizes battery life.
To make a
call after connecting the telephone, open the generator crank cover on the end
of the phone, screw the crank onto the threaded shaft. Crank the generator a
few turns, this will send ringing current to the telephone or switchboard at
the other end of the line. Pick up the handset and listen for when the distant
station answers. To transmit press the PTT and speak, release after speaking.
Operation
Telephone to Telephone Connection
The
simplest field telephone setup is a point to point operation. This can be set
up quickly and is usually used to enable a forward outpost to communicate back
to the front line or a command post (CP). The configuration is two FF33
telephones and a one pair line between the telephones[2].
The line
between the points can be run using a hand cable reel or backpack wire reel for
longer distances. The cable can be run from CP to the outpost or the reverse,
the wire reel is left at the destination since the connection to that telephone
will be made directly to the termination at the reel. The other telephone will
be connected at the origination of the line run.
The line
pairs will be marked to indicate which lead of the pair is earth (ground). The
earth end is connected to the screw terminal marked Lb/E the other is connected to the La terminal. At the other end of the line the same connection is
made.
Achtung! In the heat of action a careless jäger
can very easily snag the incoming line, which will pull the telephone off the
table, you will always snub the incoming line to a solid object. This
is the first step before attaching the incoming line to the telephone. It is
far better to snap the line than smash the 70 year old telephone.
Once the
telephones are connected a communications test should be run. The outpost rings
the CP and requests a test count. Once the outpost test is complete the CP
rings the outpost and requests a test count. This tests two way
ringing and talking. This also reminds the outpost to take steps to muffle the
ringer if needed. Wrapping the telephone in a blanket or a zeltbahn is an
effective method of reducing the volume of the ring.
Multiple
telephone to telephone connections can be set up feeding back to the same CP.
Using the patch cable each point to point connection can be jumpered
together for a three way or greater connection as
shown in this diagram:
Telephone Net Switchboard Operation
In a larger
field situation a telephone net with a central switchboard[3]
(klappenschrank) is employed. Switchboards are usually the 10 line
(klappenschrank zu 10 Leitungen),
or the 20 line variants (feldklappenschrank zu 20 Leitungen).
To the left is an example
switchboard setup. The telephone interface[4] (Amtszusatz 33) is attached to a 10 line switchboard
(Klappenschrank zu 10 Leitungen)
with two FF33s. This makes for a nice command post communications setup.
When a
switchboard is employed all lines run directly to the switchboard and all call
connections are controlled by the operator.
Below is an
example field arrangement of field telephones, lines and switchboard. Operation
of the telephones is performed in the same manner. The only difference is when
in placing a call the operator will answer and you must tell him to whom you
wish to be connected. The post you are calling from will be known to the
operator as the line will be marked on his switchboard.
[1] If the phone is closed improperly it
is possible to snap the bridge of the handset, care should be used in closing
the phone with the handset in the cradle. Always
make sure the larger microphone end of the handset is in the depression
opposite the battery end.
[2] Communications
begin to degrade if the line length is over a kilometer.
[3] Detail and operation of switchboards
is described in detail in the switchboard technical document.
[4] The telephone interface allowed the
switchboard to connect into and dial regular German Reichspost
telephones used in military offices and other locations.