Components:

R1,2,6,7,9,10 - 560 ohm, 0.25W
R3,4,5,8 - 4K7 OHM, 0.125w
T1     - BC556 or 2N3906
T2,T3  - BC546 or 2N3904

Tx is -12V when inactive. therefore the diagram correctly shows that r4 goes to tx because it uses the -12V to pull down Rx when RS232 is in Rx mode.