So here's an eye-opener. Turns out Sylvania made a TV that showed your slides, just like the way you can plug your (insert trendy i-device here) into your TV now and look at pictures or whatever. Who knew.
This can only mean that this TV is A) monstrously complicated and, as a result, B) unreliable. There must be a camera in the little slide carousel that captures the slides for display on the CRT. The cassette mechanism was put in there to provide a soundtrack to your slide show, with some kind of synchronization system - probably an audible beep or some such.
Pretty cool, for the month that it works before it goes "ping" and displays only the slide you shot of your blank TV screen.