These come with identical data but different electrical properties;
|TTL||5 Vpp||2 to 4 pin connector|
|SPDIF||0.5 to 0.6 Vpp in 75 Ω||RCA|
With a good quality cable such as RG59 long SPDIF cables can be used. I recommend the use of BNC connectors in combination with BNC to RCA adaptors.