RS232 voltage level converter box

[Tony Duell]

> It looks like a converter box that takes TTL level serial signals and 
> converts to RS232 levels, kind of like the MAXIM single chip solution 
> except that it is using 1488 and 1489 chips.

OK, such things did exist.

> 
> The problem is that it came with a PCjr, but it doesn't physically plug 
> into a PCjr.  The onboard serial port is only 16 pins, while the 
> rectangular connector here is 20 pins.  It physically doesn't work.

And the PCjr serial port is at RS232 levels anyway. The PCjr seiral cable 
is just a cahle, no intenral componnets (I have the PCjr TechRef with 
schematics...)

If it was used wit ha PCjr, then I would guess that the PCjr was 
connected to the RS232 side of this coverter, and some other device, 
using a TTL level serial port, was connected to the 20 pin header.

I can't think fo anything offhand that would have such a port. It might 
have been something very specialised (say to control or program some 
measuring instrument or something).

-tony