C64.5

               RS 232 Interface for the Commodore 64


     I have finish building a 232 interface for my C=64 and thought I
would share it with all.  I used mine with a MFJ 1270B but it could be
rewired for other things as well.  The main ic's used in this project
is the 1489 Quad Line Receiver RS cat no 276-2521 and the 1488 Quad
Line Driver RS cat no 276-2520.  The MFJ 1270B supplies a +-12 vdc
to the 1488 from pins 9 and 10 of the tnc.  The 1489 get +5 vdc from
pin 2 of the C=64 user port.

C=64 User Port          1488            1489               RS232

______________         _________       _________         ____________
B,C     RDX                             3
H        DCD                             6
K        CTS                             11
L        DSR                             8
M        TXD             12,13
N        GND               7             7                     7  SG
2       +5VDC                            14
                           11                                  2  TXD
                                         1                     3  RXD
                                         13                    5  CTS
                                         10                    6  DSR
                                         4                     8  DCD
                           1                                   10 -12VDC
                           14                                  9  +12VDC            

    Caution should be used around the  C=64  user port connection a mixup
here will blow fuse inside the C=64 or maybe worse!
External power could be used to make this interface work with a KPC 3 and 
C=64 setup.  73 de Steve  N9LOH@KD9JK.WI.USA.NA