Although the chart looks complicated, there are really only two different cables here: one where two twisted stitches are passed over each other (1 st over 1 st) either backwards or forwards, and one where a twisted stitch is moved right or left over a background purl stitch as highlighted. This is to show that all stitches are knitted through the back of the loop, they are even twisted when working a cable. Here there are no ‘blank’ knit stitches, but there is a loop symbol. Some cables, of course, use twisted stitches or other non-standard stitches, and so for this we’ll look at the chart for the ‘Twisted Diamonds’ pattern from issue 17. If you ask a better question you will get a better reply.Understanding Twisted Stitch Cable Charts
#How to make loopback cable manual#
At least in California there is nothing at the CO end to loop up, unless the carrier people put up a manual loop the DSX-1 or in the Digital Cross-Connect. The only clock source was the test equipment until it was put into service. I used A T-BERD all the time on point-to-point DS1s. When I used to turn up DS1 end links, both Telco and I could loop the NIU at the other end. All I know is I have had a few cases where unclocked T1's failed to be easily troubleshot with out changing the clocks just to allow loopbacks and that gets messy in a hurry.Ĭan you explain? Any DS1 not connected to a switch or equivalent has no clock source until equipment is connected. But this could become a ring-around-a-rosie scenario. NOTE: I suspect that some (maybe most?) equipment automagically switchs to internal clock if there is no incoming signal, meaning in that case loops from the far would work even if this device is set to use recovered clock. In this case no matter how you loop it the clock is the same. In this case both CPE are recovering clock and using recovered for Tx.
To my mind having a network clocks (which after all is a highly stable clock(strata 2 or 3)). IN this case there will be slips if the incoming data is not clocked to the same clock as the outgoing data. Most of my troubleshooting is long distance and most of my customers have no T-berd so loops to/from the CPE is the only option we have.īut keep in mind that most CPE cannot use two clocks simultaneously. In this case you would have separate clocks west and east. Now, if you wanted to test this line you could put a pair of T-berds on the line with each configured to use internal Clock for TX and recovered clock for RX. However, if we loop back site A site B will have no TX clock since its TX clock is the recovered RX clock. If we loop back site B A gets signal back and since this is synchronous to the TX clock (since it IS the TX clock) there are no clock slips. the CPE would be set to recover clock and to use recovered clock for TX. RX clock would also be from the internal clock (most equipment in my experience cannot use separate clocks for TX and RX).Īt the other end (Site B).
In that case (just like a limited distance modem) one CPE (lets call it site A)would be configured for internal clock for TX.
If the T1 does not go through a CO (which is a rare case)it would be unclocked.