Siemens SIPROTEC 7SJ61 Manual page 390

Appendix
A.3 Connection Examples
Figure A-18
1) for 7SJ64 port D
2) for 7SJ64 optionally port C or port D
390
Half-duplex operation with two RTD-Boxes, above: optical design (2 FOs);
below: design with RS 485
SIPROTEC, 7SJ61, Manual
C53000-G1140-C210-1, Release date 02.2008