This modification of Erik Hermans RS232 Programmer works
with RS232 levels at +/-6.5V and input levels at +/- 3.0V.

PIC16C84
-------I   /--I--\ BC547B
       I   I/ I  I
   RB7 I---I--I--I----I------- CTS (5)
       I   I\ I  I    I
       I   \--I--/   ---
       I      I      I I 1.5K
       I     ---     I I
       I 10K I I     ---
       I     I I      I
       I     ---      I------- DTR (20)
       I      I
   Vdd I------*-------*------- GND (7)
       I           /  I
       I         I\I  I
   Gnd I------I--I I--* Z5.1V
       I      I  I/I  I
       I      I    /  I
       I      I     + I
       I      I  I I  I
       I      *--I I--I 100uF
       I      I  I I
       I      I
       I      I  I\I   1N4148
       I      I--I I--*------- RTS (4)
       I         I/I  I
       I              I
       I   --------   I
   RB6 I---I 10K  I---I
       I   --------
       I   --------
  MCLR I---I 10K  I----------- TxD (2)
       I   --------
--------

Jens Dyekjaer Madsen,
http://www.ebar.dtu.dk/~c888600/newpic.htm
Alternate: http://www.gbar.dtu.dk/~c888600/newpic.htm