Swapping out the headsets also was a good opportunity to introduce another change to the headset. The new Dfh.b headsets installed in the tanks along with the Kasten 20 had black synthetic rubber ear pads instead of the earlier orange brown pads.
Black pads automatically came with the much awaited intercom upgrade, so that explains why the earlier type pads disappeared so quickly within a short time span in wartime photos. Theoretically the radio man could keep his old Dfh.b headset, but he must have also quickly replaced his pads to match the others, as the orange red pads must have been an unnecessary draw for sniper fire.
The Kmfb throat mikes
Along with the “b” model headsets, came “b” model throat mikes, but unlike the headsets, only the commander and the radio man got the kmfb mikes, and the driver and gunner used the old kmfa models till the end of the war.
The reason for this lies in the complicated switchboard functions made possible by combining the Kasten 20 switches and the switch on the kmfb. Although the kmfb is identical to the kmfa in design, except the plugs, which were now three pronged, the internal circuit was different in that the switches on the kmfb were not on/off switches, but rather had a switchboard function, which gave communication mode selection initiatives to the commander and radio man.
In other words, the kmfb mike was always “live” as long as it was plugged in, and if the commander or radio man did not want to be heard by others, they had to unplug themselves. Their kmfb switches shifted their communication mode, which finally brings us to the unavoidable explanation on the mindboggling, complicated switchboard functions provided by the Kasten 20.
02-15-2016 09:34 PM
Switchboard Functions of Panzerkasten 20 and Kmfb Combination
What I am about to explain is also featured at length with illustrations in the Tigerfibel as well as the Pantherfibel, so if you prefer to read them in German instead, please refer to those manuals.
The radioman was in constant connection with external radio traffic and played the role of switchboard operator of his tank for incoming and outgoing traffic. This role of “operator” boiled down to his flipping of two toggle switches on the Kasten 20 and his Kmfb mike switch.
There were two selector switches on a Kasten 20. One determined who monitored the incoming messages on the two receivers.
The default- setting for this selector was “ Funker u. Pz. Führer Empf. 1 u. Empf. 2”, which meant both the radio man and commander monitored receiver traffic. The alternative setting was “ Pz. Führer Empf. 1, Funker Empf. 2”, which split monitoring responsibilities between the two, the commander taking receiver 1 and the radio man the second receiver.
The other selector had the settings “Funk u. Bord”, and “Funk”, of which the latter was the default setting, meaning what the radio man heard was only the incoming external traffic. The other position allowed him to listen to both radio receivers and also join the onboard chatter.
How to operate the Kasten 20 in conjunction with the Kmfbs
If you seriously want to know how to switch between the various communication modes in a German tank, read on after taking a deep breath, as you need full concentration to understand this.
The various communication scenarios possible with the Kasten 20 were as follows,
(a) Standard/Default Mode
Commander, Gunner and Driver would communicate with each other, while the radio man monitored incoming traffic on both receivers. This required the driver and gunner, who were equipped with kmfa mikes to keep the mike switches engaged. The kmfb mikes used by the commander and radio man were already live without having to depress the switch. All the following operations assume this default situation as the starting point.
(b) When the Commander operated his Kmfb switch, he switched to External Communications Mode
When the commander wanted to hear the incoming traffic instead of inside chatter, he would depress his kmfb microphone switch, which gave him access to both receivers like the radio man. The commander could also access the radio man with his microphone in this scenario and tell him to switch the transmitter to send (meaning, to switch the transmitter to voice transmission if it had been in morse transmission mode.), which allowed the commander to transmit. While the commander dealt with external communications, the driver and gunner could continue the onboard communication between themselves without disturbing the commander.
(c) When the Radio man operated his Kmfb switch, the Commander got access to External Communications (initial version Kasten 20 only)
If the radio man heard something on incoming traffic that required the attention of his commander, he would depress the switch on his kmfb microphone. He would give the commander a short heads-up and the commander could now listen and communicate externally. However, this action had the drawback of sometimes cutting the commander off in the middle of his dialog with the gunner and driver, so a remedy was introduced by changing the circuit for the Kasten 20 in 1943/44. These modified Kasten 20s were identified by a red bar added to the Kasten lid.
(c’) When the Radio man wanted to get the Commander onto external traffic (applicable to Panzerkasten 20 with red bar)
When the radio man received any external messages that needed to be dealt with by the commander, he would switch the selector briefly to “Funk u. Bord” (Funk being the default) and alert the commander about this incoming traffic. This radio man’s heads up could be heard also by the other crew as well.
The commander would now depress his kmfb microphone switch when it suited him (after finishing with any instructions he was just giving to the driver or gunner) while the radio man switched back to “Funk”. The commander could now hear and respond to external messages.
If for instance the radio man had caught the commander in the middle of giving gun aiming commands, he needed to refrain from cutting in and immediately switch back to "Funk" and listen to the incoming alone and take notes to convey the message to the commander immediately after.
(d) Incoming traffic on both receivers that require attention (early version Kasten 20 only)
If important messages came in simultaneously on both receivers, the radio man could give traffic on receiver 1 to the commander and he dealt with those on receiver 2.
He did this by switching the Kasten 20 to “ Pz. Führer Empf. 1, Funker Empf. 2” (the default position being, “ Funker u. Pz. Führer Empf. 1 u. Empf. 2”), while depressing his microphone switch. Now the commander dealt only with incoming on receiver 1 ,and the radio man had receiver 2.
As soon as this need for a responsibility split was over, the radio man would switch back to “ Funker u. Pz. Führer Empf. 1 u. Empf. 2”, and after giving the commander notice, he would disengage his kmfb microphone switch to revert to default a).
Once again, this could forcibly interrupt the conversation the commander was having, so the red-banded Kasten 20 let the commander initiate the switching as described next.
(d’) Incoming traffic on both receivers that require attention (later version Kasten 20 with red band)
If important messages came in simultaneously on both receivers, the radio man had to get on the intercom by switching briefly to “Funk u. Bord” and alert the commander. As the commander switched on his microphone, the radio man needed to reset to “Funk”, and further make the switch to “ Pz. Führer Empf. 1, Funker Empf. 2” . As soon as the need for simultaneous communication ended, the radio man would revert back to the “ Funker u. Pz. Führer Empf. 1 u. Empf. 2” default.
The Pantherfibel issued in June 1944, said the radio man should keep it at "Funk u. Bord" after alerting the commander of incoming traffic (instead of going back to "Funk" as just explained), as that setting allowed the commander, driver and gunner all to listen to radio receiver 1 together, while the radio man listened to receiver 2. Although the incoming signals were thus split, all on board could communicate with each other on the intercom.
This, however, meant that the driver and the gunner also could transmit on the radio, if their kmfa mikes were kept on, so they needed to exercise discipline not to clutter the radio waves. The "Funk" position would have cut the diver and gunner off external communication.
The c’ and d’ scenarios above were provided as printed updates to the manual to be pasted over the out-dated descriptions.
(e.) Radio Silence
Receivers and transmitter were to be turned off and the Kasten 20 switched to "Funk u. Bord". This allowed onboard communication between all 4 crew on the intercom system, while observing radio silence.
As seen above, the switch on a Kmfa was only for on and off, but on the Kmfbs they worked like a remote control access to the outside world.
So though the arrival of the Panzerkasten 20 allowed all to use the same headphone, the complexity of switchboard functions brought in the need to use two different models of throat mikes within the same tank.
1944/45 Models of Headset and Throat Mike
Kmfa and Kmfb mikes were used in parallel until the end of the war, but for the Kmfb there was a simplified version called the Kmfc that omitted the push button on the side and reduced the size of the switch box to approximately 50%. Not much is known about this version of microphone introduced in 1944, but as it was with a 3-pronged plug, we can assume that it had the same function as the Kmfb. Also towards the end of the war, switch boxes normally associated with throat mikes for the field telephone also seemed to be built into Kmfbs.
As for headsets, a notable compromise observed in 1944/45, in light of material shortages, was the omission of leather covering from the headband (Bügel in German), particularly commonly seen on 1945 produced headsets.
Bender’s book, “The Panzertruppe” claimed that a model called Funkhaube A (Radio cap model A) that combined the headset and throat mike was further introduced in 1944, but I have never found documentation to support this claim, nor have I seen any original examples likely to be this model.
This was a logical step, however, because the Luftwaffe flight helmets had already combined the two and equipped it with a single quick release plug that could be easily disconnected when there was a need to escape quickly in a fire. The system employed in Panzers was less suited to deal with such emergencies (2 plugs to disconnect or headset and mike to remove without getting tangled up in the cords ) and also could not be worn under a helmet, so a setup in the flight helmet style would have been a very plausible next step. However, until further evidence surfaces, Funkhaube A needs to remain a mystery.
Communication hookup points for Commander and Gunner
The driver and radio man connected their headset and mike to the Kasten 20, but for the commander and gunner hookup points were required in the turret. Here I will show you what they looked like.
Here is a rare Z series Kasten used between 1936 and 1941.
Here is one for use with the Kasten 20 after 1941
Lastly, a Kasten 2 from a command tank. Note that, because they had so many radios onboard, they had to go back to using light signals for alerting the crew.