Discussing about machine order telegraphs, I would like to mention one thing.
The type VIIC U-Boat manual (
http://uboatarchive.net/Manual/Manual.htm) on page 181 describes the following item:
"Rudder order telegraph and rudder angle indicator system"
This piece of equipment is related with the emergency (hand) steering in case of main rudder electric control failure. In such situation, the helmsman took his station in the aft torpedo room, near the air compressors, at the emergency steering station. There was located the hand wheel for driving the main rudder. The helmsman took with him the detachable gyro-compass repeater, to know the current course.
As we know, the helmsman received two kinds of orders: heading order (i.e. "on course 71 deg" or "on east course") and rudder order (i.e. "hard port" or "15 degree starboard") related with the rudder angle. If the helmsman was in the aft torpedo room, the heading order was passed to him verbally. But rudder orders could be passed by means of the "Rudder order telegraph" which was coupled with the "Ruder angle indicator system".
The rudder order telegraph system consisted of (as described on page 181 of the manual) from the rudder angle indicator coupled with the rudder order transmitter located in the control room and from the rudder angle indicator coupled with the rudder order receiver located in the aft torpedo room.
Unfortunately, I have never seen any photo related with the type VIIC U-Boat, showing such system. Similarly, it can not be found on board of U995. I guess, that the simple rudder angle indicators (without rudder order transmitters and receivers) were installed due to cost/labour saving purposes.
However, such device can be observed on the board of U505. I have attached the photo "U505 main rudder order telegraph.jpg", which shows the rudder angle indicator with the rudder order transmitter. You can see two pointers (one above the other) - one showing the current rudder deflection, the second is the rudder order. Below, you can see the knob for setting the rudder order. The label at the bottom of the dial says: "
Hauptrudder Telegrf Geber Lagenzeiger" that means "Main rudder order telegraph transmitter and indicator".
At the emergency steering station (in the aft torpedo room) was installed the similar unit, but without the knob.
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Regards
Maciek