Serial Cable for Old HP-48G Series

Connect your HP-48GX, HP-48G+, HP-48G, HP-48SX, or HP-48S to your computer with this high quality 9 pin (PC) to 4 pin (Calc) serial cable.  This cable is not suitable for any other calculators except those listed above.

Looking at back of HP-48:

    ---------
   | 1 2 3 4 |
    \_______/

Here are the pinouts for the HP-48G serial port:

                  4 3 2 1
     /------------|-|-|-|----\
    |   48SX                  |    Pin   Function    Standard RS232 pin eqv.
    |   ___________________   |                       (25 pin connector)
    |  |                   |  |     1  Chassis Ground       1
    |  | 4:         "THIS" |  |     2  Transmit Data        2
    |  | 3:           "IS" |  |     3  Receive Data         3
    |  | 2:          "THE" |  |     4  Signal Ground        7
    |  | 1:       "SCREEN" |  |
    |   -------------------   |
    |                         |
    | [A] [B] [C] [D] [E] [F] |
    | MTH PRG CST VAR  ^  NXT |
    |     .  .  .  .  .  .    |

If you're making a cable, just make a standard null modem cable.
(reverse RX and TX)

      HP-48 pin           RS232 pin

   CHG   1  - - - - - - - -  1  CHG     Chassis ground does not
                                        actually have to be connected.
    TX   2  ------\ /------  2  TX
                   X
    RX   3  ------/ \------  3  RX

   GND   4  ---------------  7  GND