Serial Cable for Old HP-48G Series

Looking at back of HP-48: hp48g pin out

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.

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

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

                  4 3 2 1
     /------------|-|-|-|----\
    |   48SX                  |    Pin   Function    Std RS232 pin
    |   ___________________   | 
    |  |                   |  |     1  Chassis Ground       1
    |  | 4:         "THIS" |  |     2  Transmit Data        2
    |  | 3:           "IS" |  |     3  Receive Data         3
    |  | 2:          "THE" |  |     4  Signal Ground        7 (DB25)
    |  | 1:       "SCREEN" |  |                          or 5 (DB9)
    |   -------------------   |     DB25 = 25 pin connector
    |                         |     DB9 = 9 pin connector
    | [A] [B] [C] [D] [E] [F] |
    | MTH PRG CST VAR  ^  NXT |
    |     .  .  .  .  .  .    |

HP-48 pin RS232 pin

   CHG   1  - - - - - - - -  1  CHG     Chassis ground does not
                                        actually have to be connected.
    TX   2  ---------------  2  TX

    RX   3  ---------------  3  RX
   GND   4  ---------------  7  GND (DB25) or 5 (DB9)

hp48g cable