Voice data on a T1 is sampled at 11Khz, though, not 8 to try and maintain some level of quality signal.
11kHz? Is it oversampled then and then spit out at 8kHz?
E&M uses A&B bits which are the low order bits of each frame for individual channel signalling. ISDN uses the D channel to convey this information for the other 23 channels, on a PRI or the other 2<?> on a BRI.
ESF robbs bits for all timeslots every 6th frame, not every frame. That gives you A, B, C and D bits but IIRC the C and D bits are "for future use" and are often (but not necessarily) just copies of the A and B bits. ISDN BRI gets 64k because, as you already pointed out, there is not robbed bit signalling going on and the D channel is used to cover the signalling on the associated B channels. I don't recall what the actual numbers are but I believe you're correct: 23 channels on ISDN PRI and 2 on ISDN BRI.
I think at this point I have an insatiable hunger to find out the exact answer, and I work with several really good telecom geeks, so this coming Monday I'll ask one of them and point to this story and find out how badly mistaken I was.
Me too. (not how mistaken you (and I) possibly are, but rather what the CORRECT answers are. :-)
I will say though, if you add the two sigbits into my numbers which you have to do, the ISA bus is still fast enough. I know this from experience, as we run 8 T1's, 4 E&M 4 ISDN on a single ISA bus and have no problems. I don't think our boxes have ever run 100% capacity, but they've gone over the 75% capacity I argued in my earlier post.
I was arguing in favour of there being enough bandwidth on the ISA bus. I guess we're both on the same side here. :-)
I've always been keen on telecom. When I actually found out how T1/DS1, DS3s and DS4s worked it kinda took the magic out of it all though. Actually I'm more interested in the communication between the DSU/CSUs than the actual data being transferred. :-)
You being more a telecom geek than I, perhaps you can answer this for me: Why on earth do I need two DSU/CSUs at my end? Bell Canada has their own but has a second DSX-11 port on it which I have to plug into my own DSU/CSU which finally has the desired serial port to attach to the router. I understand why Bell would want their own DSU/CSU (diagnostics, they can control the quality of the equipment actually screaming on the wires, etc.) but why not just give a sync. serial port out the end instead of another T1 port? It seems a waste to go 80km to a DSU/CSU only to go another 5 feet to ANOTHER DSU/CSU to give me a serial port.
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