Hi, All.
I've just commissioned the remote band-switch motor on a 1944 Bendix
RA 10DB aircraft receiver, controlled from the remote unit that I had
to partially rebuild. I had the schematic but no cables so I had to
make them - what a pain! But what an incredibly clever servo system!
Changing the band at the remote invokes a whirring and clanking as the
motor drives the band switch though its travel to the right point.
Here's a summary I wrote from the original 1944 documentation. Enjoy!

2-1-2-10 Band Change Circuit (summary by RJ from original
documentation)

-- Motor drives switches S1 to S6 change the band. Mechanically:
-- Motor armature to worm drive, ganged to a common shaft, crank arm,
locking cam and control cam
-- Motor control switch S8 rides on the control cam
-- Crank arm and and locking cam operate a Geneva disc (What is
this? RJ)
-- Hollow shaft of Geneva disc is slottrd at one end to engage the
locking pin of a long drive shaft
-- Long drive shaft passes through the Geneva disc, drives the motor
positioning switch S7 and runs through the RF coil and can assemblies
-- Band change switches S1 to S6 operate together on this shaft (see
note to section 6-4-1-2)

-- Remote control unit band selector switch S101B selects band
-- Band switch motor B1 is energized by completion of its return
circuit to ground through contacts on S101B and the shorting contact
on S7
-- Motor B1 drives the crank arm through one or more complete
revolutions (depending on band selected)
-- This steps the Geneva disk to the desired position
-- At this point the motor is automatically de-energized by an open
slot in the shorting contact of switch S7
-- Exact position control is obtained by the cam-operated motor
control switch S8
-- When motor B1 is at rest the arm of S8 is on step 2 of the control
cam and all contacts are open
-- When motor B1 starts the arm is first raised by step 3 of the cam,
closing the upper contacts
-- These contacts close the reversing field of motor B1 to a selected
rotor on the positioning switch S7
-- These selected [S7] contacts connect to a non-grounded position on
S10-1B, thus the motor continues to run
-- When the arm of switch S8 drops to step 1 of the control arm, the
upper contacts are opened and the lower ones are closed
-- The closing of the lower contacts provides an additional path to
ground to keep motor B1 energized after the opening of selector switch
S7 by movement of the Geneva disc.
-- When the crank arm has been driven past the Geneva disc, engaging
the locking cam with the arc of the disc, the control cam raises the
arm of motor control switch S8 to step 2, opening all contacts.
-- Motor coasts to a stop
-- If motor coasts past step 2, the upper contacts of S8 will be
closed, effecting a return to ground for the motor reversing field
through S7 and S1010B.
-- Motor will then reverse to drive the cam back to the proper
position with all contacts of S8 open and the motor at rest.

Phew!
Now to sort out the AVC/MVC function (remote unit switch) and check
the RF/IF/detector/audio.
Cheers,
Roger