The BC-189 is not as capable a receiver as the BC-224-A. Bandswitching was accomplished by replacing the tuning coil drawer, for example, and interpolation charts were required to understand what frequency the receiver was tuned to, but it weighed less and was simpler to operate for non-technical airmen.
GE also produced a smaller transmitter for aircraft use that was sort of in-between the liason and command set in power output, called the BC-307. With the BC-224-A, the combination was labeled the SCR-238. The transmitter is shown below. This particular unit is a BC-307-A - the date on the tag is 9/12/1936 - though they were manufactured in a -B model up through 1942. The scale may be misleading to those who are familiar with the BC-375 sized transmitters - this cute little thing is only 14" tall!
The frequency tuning charts were made out of .038" aluminum, with black silk screened lettering on them. On top of this transmitter can be seen one of the blank charts that have been reproduced on the mill prior to silk screening. Actually, this particular example is not as bad as it looks in this photo. The external panels will need to be repainted (unfortunately), which means all the engraving will have to be done again, but internally it is in fairly nice shape.