extention of 6ES5734-1BD20 TTY/RS232 converter cable

We are using 6ES5734-1BD20 TTY/RS232 converter cable for communication between S5-115U and OP77 Panel.This converter cable max.length is 3.2m and now we want extend the distance nearly 30 m. between Plc and OP.I looked Siemens site there is a information.
in www.elv.de order no: 68-176-10 (for a mx.distance 1000m TTY/RS232 converter) but ''The article you requested is no longer in our assortment ''message is shown.Is there any solution for this? Thanks in advance...

Siemens :
http://support.automation.siemens.com/ww/llisapi.dll?func=cslib.csinfo&objId=23522061&load=treecontent&lang=en&siteid=cseus&aktprim=0&objaction=csview&extranet=standard&viewreg=WW

We once had a similar problem.
We didn't take a Siemens extension cable.
We chose to use a Phoenix Contact module. PSM-ME-RS232/TTY-P

We placed the module close to the panel and then ran a 35m shielded twisted pair cable to the PLC.
Connectors were selfmade with Phoenix contact connectors. 9 pin and 15 pin.
I can't find the pin-outs we used since the setup has been removed over 6 years ago. But I'm sure they can be found on the internet.

I'm not a Siemens guy but here's my take on it

-quote from linked page above-

Instructions:
SIMATIC HMI Windows-based panels do not possess a TTY (20mA) interface which is needed for communication with a SIMATIC S5 PLC.

Exception:
The MP 370 operator panel possesses a TTY interface. Furthermore, the interface can be switched between V24 and TTY on a panel PC in the BIOS.

-end quote-

V24 means RS-232 (comes from the ISO2110 standard V.24)

The TTY they are referring to is also called "Current Loop", not to be confused with an analog 4-20mA current loop.

A TTY current loop drives current signal much longer distances, l000m, but an RS-232 voltage signal is limited to about 15m.

TTY-RS-232 converters convert from a voltage RS-232 to a current loop signal.

Sometimes they're used in pairs when two RS-232 devices are a long distance apart, with one converter at each end, using the RS-232 port on the device but communicating over the long distance with the current loop.

If either the S5-115U and OP77 have a port that can be configured for TTY current loop, then a single TTY/RS-232 converter will work.

If neither the S5-115U nor the OP77 have TTY, then using a pair of current loop converters will work, with the current loop carrying the signal over the long distance.

The 115U has a TTY port.
The OP77B has an RS232 port.

I think it is a good idea to try the Phoenix Contact module that Jeebs suggested.