Phone plug help needed - Page 1
Forum section: electronics / beginners

author: Shock
author_rank: Super Contributor
timestamp: April 24, 2014, 07:01:43 am
content: Anyone know anything about these phone plugs?Am looking up a suitable replacement for the WECo 310 and the HP manual shows it also as a PJ-051R.The top plug (3 conductor) is labeled both PJ-051R and M642/2-2 (which I assume is the military spec).The bottom Pomona plug is labeled a WE 310 to BNC (2 conductor, does not employ the sleeve).I have two questions:1. The top plug looks like it has two separate conductors at the ring compared to the pomona, what is this? Is the Pomona plug correct or is this a difference in specs?2. I was going to make a dual purpose patch cable (audio frequencies) for balanced and unbalanced use. Is there any benefit in using all 3 "conductors" and chassis ground the shield to the instrument end only?Should I be using twisted signal cables for the balanced or will a double shielded coax be the thing?

author: fcb
author_rank: Super Contributor
timestamp: April 24, 2014, 10:46:34 am
content: Quote from: Shock on April 24, 2014, 07:01:43 am1. Not sure why it appears to have 4 conductors, it probably doesn't use 4 conductors.2. Use twisted pair if you can - especially if you using balanced electronics. If you're not using balanced electronics then it won't matter much. As for grounding - that is a more complex question, and will be very dependent on your system design.BTW: These jacks are called 'bantam jacks'.

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 24, 2014, 11:04:23 am
content: Quote from: Shock on April 24, 2014, 07:01:43 amThat extra metal "ring" was provided for long-term, heavy-duty protection in telephone switchboard use. Where those plugs were inserted and pulled out perhaps hundreds of times every day. (Back before the days of automated phone systems where the user would dial the number for themselves and relays would make the proper connection.)The extra metal ring was not electrically connected to anything.QuoteWe commonly use ordinary "mic cable" which is flexible, shielded, twisted pair. It is customary to connect the shield at both ends of a patch cable, and implement whatever ground-lift, etc. in the wiring between the patch bay and each piece of equipment. The whole area of shielding and grounding is a very sticky wicket with galaxial political ramifications.That is a "long-frame" switchboard/patchbay version of a 1/4 inch phone plug.Bantam phone plugs are a smaller variety, not interchangeable with the model you show in the photos.

author: Shock
author_rank: Super Contributor
timestamp: April 24, 2014, 11:26:03 am
content: Quote from: fcb on April 24, 2014, 10:46:34 amQuote from: Richard Crowley on April 24, 2014, 11:04:23 amYes I was about to say the Bantam seems a different beast, 4.4mm diameter not 6.35mm on the WE 310, PJ-051R.Thanks for the info. I have looked at how the jacks/sockets work and that makes sense.

author: fcb
author_rank: Super Contributor
timestamp: April 28, 2014, 09:39:33 am
content: Quote from: Shock on April 24, 2014, 11:26:03 amQuite right - spent to much time recently playing with bantams.