I am part on the Cave and Cliff Unit of rescue service in TN. We often spool out a 2 conductor wire and connect field phones from Norway called TP-6N-C. We use these to communicate far distances underground where radio doesn't work. They are vital to rescuing in caves. The TP-6N phones ((data here) are fairly manageable but we'd like to start working on a smaller option that would fit in a small 3d printed handset or pelican case.
I was curious if anyone on the forum could possibly give a little time and weigh in on if using an Arduino would be feasible. I'll give a little info on the requirements.
The existing phones are run on 3 D cells, so 4.5V. They send an analog signal along the wire and work with pretty much any old field phone, even hand crank ones, and the 'shoe phone'. I'd need this Arduino phone to receive that analog signal, put it to a speaker, pick up audio from a mic on push to talk and send it back along the wire with a similar voltage/amp so it's compatible with any of the phones.
The line usually has many phones attached to it at once. I'm not really sure about the specs of the signal on the wire. I don't have an oscilloscope yet.
This would likely be a huge project for me and require a ton of learning. I'm very comfortable making small circuits of LEDs and maybe a simple relay circuit, but that's about it. Programming abilities are at beginner levels.
Paul__B:
So you fancy making a substitute for an extremely rugged, durable and well-tested system using batteries deliberately chosen for a long service time?
Indeed so, which does beg the the question as why one would embark on a 'huge project', what are the benefits ?
Thats not intended for as a criticism to the OP as such, but you would expect 'large projects' to have good objectives.
I work in telecoms, have done all my life. I cannot see a role for an Arduino. Maybe a few op-amps or something like that, although the original basic design of a telephone goes back many years and has not changed much, just more up to date components.
I also used to be a caver* so have some idea of the conditions electronics have to withstand in a cave - the have to be well protected from water ingress and physical damage. Do you really want to make a rescue trip dependent on home made electronics?
Thank you all for the replies. I think you fully answered my question.
Just to reply to some of the comments:
We aren't replacing the TP-6N field phones from service but instead want to add a handful of phones that are smaller and lighter. I know this would be at the expense of ruggedness, functionality, and comfort of use. We would stuff them in the cave packs or Darren Drums (ridged containers) of underground commanders and team leads. With sometimes miles of cave and slow progress through them we thought it would be a good option to give those few people the ability to patch into the comms line that's already run and make contact without having to reach the next comms station in the cave. So they would be used sparingly and serve a slightly different purpose of not being a fixed location phone and the TP-6N would be the standard workhorse.
PerryBebbington, we would indeed use home made electronics during a rescue for this purpose. The existing solutions are too big for team leads and underground coordinators to bring into cave, so right now they go without. We also use other electronics that are home made, although by a much more competent person. We have some small electronics that can patch the cave comms into a cell phone, so in cave medics can talk directly to someone not on site, like a doctor at the hospital, etc. I get your point though, for sure. Definitely something to consider. Also glad to hear you've never needed a cave rescue! It can be kinda fun being wrapped in the litter like a burrito but only for a short bit.
The TP6Ns main wire from the handset to the phone are turning to dust inside. They have some sort of waxy jacket on the conductors and it crumbles as soon as you touch it. A lot of the phones are starting to short out inside and cause issues with comms. I was able to replace that wire though and retain (hopefully) a lot of the waterproofing and strain relief on the cable. It was a fun project for me!
Anyways, thank you all again for your comments and reading my post. I really appreciate that.
it sounds like you want to somehow tap into the communications wire at places along the wire path. If so, have you tackled that issue? Another approach might be to use the wire as a long antenna to which RF units can use.
The TP6Ns main wire from the handset to the phone are turning to dust inside. They have some sort of waxy jacket on the conductors and it crumbles as soon as you touch it. A lot of the phones are starting to short out inside and cause issues with comms.
For a device that is supposed to be reliable and save lives, that is really disturbing.
Is this some cheap knockoff, or just a sign of our times?
I guess if I'd carried on caving I might have joined cave rescue when I became experienced enough. It was my brother who got me into it but when he stopped I stopped. It was a long time ago. Great fun
