IC1 = TSOP 1738
+-----------------------+                             R1 (4k7)
|           DATA (3) -> +--------------------------------+------------o DCD (1)
|                       |                 _______        |
|      ______________   |                | 78L05 |      | |   D1 (1N4148)
|     /                 |    +-----+-----|OUT  IN|--+   | |
|    (                  |    |     | +   |__GND__|  |    |      | /|
|     \__________ + (2) +----+   -----       |      +----+------|< |--o RTS (7)
|                       |        -----       | IC2              | \|
|                       |          |         |
|                 - (1) +----------+---------+------------------------o GND (5)
+-----------------------+      C1 (4µ7F)