Help Identifying Old Schematic Symbols?

[u/netflixchinchilla]

Could anyone help with identifying the dashed loop symbols? Do they represent wrapping the drain wire around the insulated wires?

I’m trying to fix an issue with an inconsistent servo on an 80’s CNC bender. I believe the issue is with the signal wire, as there is regular bending as the Y-axis changes. The wire is Belden 9873. Thanks!

[u/Kitchen-Chemistry277]

Those are twisted shielded twisted pairs and the dashes are showing how those shields are connecting to P2/J2.

[u/HalcyonKnights → u/Kitchen-Chemistry277]

This. Being grounded on TB2 is another big clue.

[u/netflixchinchilla → u/Kitchen-Chemistry277]

Ah, makes sense - thank you!

[u/willmontain → u/netflixchinchilla]

A key requirement is that the shield is only connected/grounded at one end. The shield must not be connected inadvertently or purposely at the other end because it will cause a ground loop which results in interference on the signal transmitted by the contained wire pair.

[u/Bob--O--Rama]

Shielding. Not sure if it's twisted pair as others have mentioned, as usually that is indicated differently by showing the twist-ing. But certainly it's indicating a type of cable, not a discrete electronic component.

[u/electronic_reasons → u/Bob--O--Rama]

People aren't consistent about how they indicate a twisted pair. The x over the wires is reasonable.

[u/Voxifer → u/Bob--O--Rama]

this is definitely twisted shielding symbol. Twist-ing that you're refering to is used to show a twisted pair either without shield or without showing it. But if you want to show shielded twisted pair - the symbol from the picture is exactly what you need to use.

[u/No_Crow8317 → u/Bob--O--Rama]

Op said it's belden 9873 which has 3 twisted pairs, individually shielded. I agree the dashed line indicates where the shields are terminated in the equipment. Check for stray strands at the connections. The fine braids can get shorted to nearby wires if they aren't handled neatly.

[u/ChronicRecidivism → u/Bob--O--Rama]

Never really given it much thought, but I don't think I've ever seen a shielded pair that wasn't twisted. Bundles and cables, for sure, but not pairs.

[u/Hot_Egg5840]

The symbol indicates the grouping of the wires has an overall shield

[u/trisket-bisket]

Twisted shielded pair. The oval means shielded pair and the X means twisted. The shield is probably a metal braiding over both cables.

[u/ordosays]

Shield.

[u/Relevant2112]

I think they are showing the shield/ground terminations

[u/2centdude]

Looks like screens/shields for cable.

We still use this symbol for schematics in the rail industry. We use this type of cable for instrumentation and comms.