Very pleased to have found Dux Computer Digest and Forum. Your clear indication helped me to quickly arrange cable wiring for Ethernet 10Mb interconnection of PCs.
Now a question related to making cables for ISDN (Bus “S”). Base Access ISDN (2B+D) arrives into my house to a Network Terminating (NT) box.
Bus “S” ISDN is available from Box through RJ45 socket. Presently, PC is near to NT box, and 1-meter flat cable having RJ45 at both end connects NT box to ISDN modem card (internal to PC).
I would like to extend to some 20 meter ISDN cable. As I see, it is a 4-wire connection that uses 3rd to 6th out of 8 contacts of RJ45. My questions are:
1. How is the basic schematic of “S” bus connection? Do the 4 wires mean 2 pair, of Tx resp. Rx, such as for LAN? How is wire schematic, one pair to 3th and 6th and the other to 4th and 5th contacts, or else (3 to 4, and 5 to 6)?
2. It is useful/mandatory that the 4 wires be two twisted pairs (for long distances), e.g. using a 4-pair cat5 cable?
3. Eventually, I’d like to use the 2 pairs, actually left free in a 4-pair (cat5) cable of LAN -10Mb, for having LAN + ISDN in the same 4-pair cable. Is this possible, provided to decouple at both ends into separate cables LAN and ISDN (with use of available decoupling small boxes having RJ45 jack/sockets)?