[Sean]

I understand your confusion. The 1942 phonographs are completely different animals from the 1941 models except for the tonearm. Here are the interconnections for the two model years (if I remember the 1941 correctly):

1941:
Two wires come directly out of the chassis and connect to the screw terminals on the rear of the phonograph shelf. These are for power to the tonearm lamp. There is an interconnecting cable with the Motorola style plug that plugs into the jack on the chassis on one end and into the transformer on the other end (I don't remember what the connector was but it may have also been a Motorola style). There is a cable hardwired into the transformer on one end with an RCA style plug on the other end that plugs into the RCA jack on the back of the phonograph shelf. This is the audio from the tonearm photocell.

1942:
There is a 4-conductor cable hardwired into the chassis with a 5-pin (only 4 pins are used) speaker connector on the other end. This contains two wires to power the tonearm lamp and two wires to bring the audio from the photocell back. In the middle of this cable is the smaller 4-pin connector that plugs into the transformer. The audio from the photocell goes into the primary of the transformer and comes out through the secondary that is connected to the radio.

So, what you would need to do is come from the RCA jack on the back of the phonograph shelf and go into the primary of the transformer (two closer pins of the 4-pin connector on the transformer). Then come out of the secondary of the transformer (two further separated pins of transformer connector) to go into the Motorola jack on the back of the chassis.

The home recording unit has a crystal cartridge with a cutting stylus. The stylus actually cuts the groove and audio into the surface of a blank recording disc. The audio source can be either the radio or a microphone that connects to the jack on the transformer. In the case of the microphone the audio is passed through the transformer into the phonograph amplifier and then to the audio output tubes. The audio is pulled off of the output transformer to drive the recording cartridge.