Instructions:
For serial transfer via the V24 interface you should use only the cable TAG 6XV1 440 - 2K ... . The following length code applies:

6XV1 440 - 2K x ab

x = multiplier
x = E => 0.01m
x = H => 0.1m
x = N => 1.0m

ab = length code
ab = 10
ab = 12
ab = 15
ab = 16
ab = 20
ab = 25
ab = 32
ab = 40
ab = 50
ab = 60
ab = 63
ab = 80

Resulting length = Multiplier * Length code

Example:
Placing an order for a cable with a length of 1.5 meters.
The following order number results: 6XV1 440 - 2KH15
Multiplier H => 0.1m, length code = 15 => resulting length = 0.1m * 15 = 1.5m

When ordering, please note that the maximum cable length of 15 meters must not be exceeded.

If need be, for test purposes you can also use a cable that is wired as shown in the following figure.

Connector 1: 15-pin Sub-D male, V24
Connector 2: 9-pin Sub-D female, V24

Notes:

1. Cable: 5 x 0.14 mm²; shielded; max. length 15 m.
2. Shield connected on both sides over a wide area.
3. This and other pin assignments are available in the manual "SIMATIC HMI Communication", in the chapter entitled "Interface Assignment", Entry ID: 1137086

Fig. 1