Single wire, earth-return phone circuit diagram

6 posts / 0 new
Last post
YuvalS
YuvalS's picture
Offline
Last seen: 10 hours 36 min ago
Joined: 09/26/2018 - 10:39
Posts: 654
Single wire, earth-return phone circuit diagram

Hey guys,
Not lights related (hence in the off topic forum ) but since many of you have electronics knowledge I thought maybe I can find some help here.
I want to build a single wire, earth-return phone for long distance (1000s of meters) for using in cave rescue operations.
All circuit diagrams available online are in Russian or very old so some components are hard to find.

If you have any source for update circuit diagram please share
TIA

My FW repository

My BLF/OL contest entries: 7th 8th 9th | 10th |

amishbill
amishbill's picture
Offline
Last seen: 2 years 6 months ago
Joined: 05/01/2019 - 10:03
Posts: 714
Location: GA

I don’t have a reference handy, but I bet a military 2 wire field phone reference might have what you need.

DIY LT1 battery wrap image. "PDF on Google Drive":https://drive.google.com/open?id=1IHIEOi1NXu868IYNCzIM7D2Ulpxchmww

Fresh Sanyo NCR18650GAs already wrapped "for sale HERE":http://budgetlightforum.com/node/69120 if you like.

YuvalS
YuvalS's picture
Offline
Last seen: 10 hours 36 min ago
Joined: 09/26/2018 - 10:39
Posts: 654

amishbill wrote:
I don't have a reference handy, but I bet a military 2 wire field phone reference might have what you need.


Military 2 wire field phone is a good solution but I am looking for a single wire circuit in order to save half of the wire required 

My FW repository

My BLF/OL contest entries: 7th 8th 9th | 10th |

amishbill
amishbill's picture
Offline
Last seen: 2 years 6 months ago
Joined: 05/01/2019 - 10:03
Posts: 714
Location: GA

you misunderstand – two wire phones are the simplest, and if any can, they are the mostly likely to be able to use a common earth ground.

DIY LT1 battery wrap image. "PDF on Google Drive":https://drive.google.com/open?id=1IHIEOi1NXu868IYNCzIM7D2Ulpxchmww

Fresh Sanyo NCR18650GAs already wrapped "for sale HERE":http://budgetlightforum.com/node/69120 if you like.

Joshk
Joshk's picture
Offline
Last seen: 8 months 2 weeks ago
Joined: 09/09/2015 - 12:12
Posts: 2719
Location: USA

He’s asking to use the earth itself as the second wire. I don’t think the audio quality will be acceptable in a life-or-death rescue.

YuvalS
YuvalS's picture
Offline
Last seen: 10 hours 36 min ago
Joined: 09/26/2018 - 10:39
Posts: 654

Joshk wrote:
He's asking to use the earth itself as the second wire. I don't think the audio quality will be acceptable in a life-or-death rescue.


This method is very common among cave rescue teams.
Double wire or wireless systems also have cons Sad .
Unfortunately commercial systems are no longer available but many rescue teams build their own systems 

http://fieldphone.blogspot.com/

http://www.speleonics.com.au/business/michiephones/index.html 

My FW repository

My BLF/OL contest entries: 7th 8th 9th | 10th |