Schaltung des HamComm-Interfaces nach DL5YEC

                                                                RS-232C
         Receive Circuit                                         25  9
                                                                pin pin
                        IC1 TL071                   D1
                         or LM741 -------*--------*-I<--*--< DTR 20  4
                                  |      |        | D2  |
                             3 |\ |      |      ---->I---
             >------||---*-----|+\ 7     |      | |
                    C1   |     |  \______|______|_|________> DSR  6  6
                  0.1uF  |   2 |  /6     |      | | D3
                         |  ---|-/       |      | --I<--
           Signal        |  |  |/ |4     |      |   D4  |
           from          /  /     ---*---|------*--->I--*--< RTS  4  7
           Receiver    R1\  \R2      |   |
                     100K/  /100K    |   | +
                         \  \       === === C2,C3
                         |  |       === === 10uF
                         |  |      + |   |  16V
             >-----------*--*--------*---*-----------------> GND  7  5

         Transmit Audio Circuit
         (omit for receive-only)  R4       R5         R6
                                  15K      15K        10K
                      --------*--/\/\--*--/\/\--*-*--/\/\--< TxD  2  3
              C4      |       |        |        | |
             0.1 uF   / R3    |        |      D5| |D6
         <----| |---->\ 10K  === C5   === C6    - v
          MIC         / var. ===.022  ===.022   ^ -
          Socket      |       |  uf    |  uF    | |
         <------------*-------*---*----*--------*-*--------> GND  7  5


         PTT Circuit
                                  C      (omit for receive-only)
         PTT <-------------------\
                           Q1     \I B       R7     D7
                           2N2222  I--------/\/\----I<-----< RTS  4  7
                                  /I         1K
                                 v
                                 | E
             <-------------------*-------------------------> GND  7  5


         FSK Circuit
                                         (omit for receive-only)
                                  C      (optional for transmit)
         FSK <-------------------\
                           Q2     \I B       R8     D8
                           2N2222  I--------/\/\----I<-----< DTR 20  4
                                  /I         1K
                                 v
                                 | E
             <-------------------*-------------------------> GND  7  5


         D1-D8 = 1N914 or 1N4148



                         +V out
                       8  7  6  5
                       |  |  |  |    Operational Amplifier
                     |------------|
                     |            |  LM741 or TL071
                     |            |
                     |-|          |  DIL-8 package, top view
                       |          |
                     |-|          |   +V = positive supply
                     |            |   -V = negative supply
                     |            |   -I = inverting input
                     |------------|   +I = non-inverting input
                       |  |  |  |    out = output
                   Pin 1  2  3  4
                         -I +I -V