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# format auto-updated on access: Tue 02-Mar-2021 10:10:50 +00:00

# sandbox: Journal 113 has gone to press and is due for publication in March 2021
CREG Journal 113 (0-24)
This issue has a cover date of March 2021 and was published on 1 March 2021.

Front Cover (1)
Joe Mitchell (right) uses the Caveatron to scan out of a small side passage in Robber Baron Cave while Gregg Williams (left) holds a reflective card on station. Photo: Albert Parvin

Contents (2)
List of contents and masthead information.

News and Notes (2)
A New and Open Cave Radio, Graham Naylor.

Caveatron: An Integrated Cave Survey and Lidar Scanning Instrument (3-7)
With the Caveatron now well established in the caving community, Joe Mitchell describes the current state-of-play of this DIY surveying and laser scanning instrument, and provides several examples of how it's reaped benefits.

Communications Choices for Cave Rescue (8)
Tony Haigh considers communications options for cave rescue, with many of the arguments applying equally to expedition communications.

Handheld Laser Scanners: a Market Overview (9-11)
Several companies now offer portable 3D laser scanners that are potentially suitable for cave surveying. Mike Bedford takes a look at these products and presents an overview to allow potential users to draw up a shortlist.

Update: Battery Polarity Protector (12)
Further to his notes on building rugged equipment, David Gibson describes a simple addition to a battery connector that prevents cells being inserted in reverse.

Correction (12)
Correction to David Gibson's Letter regarding Addressable Electrodes in Journal 112.

Update: Pressurised Enclosures (12)
As a follow-up to his notes on building rugged equipment, David Gibson further describes the use of a pressurised enclosure to prevent moisture ingress.

Building Blocks (13-14)
The ubiquitous USB interface offers both solutions and problems for use as a power source, by Tony Haigh.

Web Watch (14)
Peter Ludwig offers another eclectic selection of Internet links. From power storage, via USB chargers, to a new microcontroller.

We Hear (15)
Roundup of news and events: Mike Bedford brings us the latest to impact the world of cave radio and electronics. Molecular Communication, Ambient Soundtracks, Micro LEDs to Offer Exciting New Opportunities.

Energy Harvesting with Electrets (16)
David Gibson envisages a portable energy-harvesting device utilising a wristwatch-style automatic winder, with the mainspring driving an electrical power generator that uses an electret material. The mainspring provides a method of regulating the power transfer, not unlike the concept of 'power matching'.

GNU Radio: Resource Issues (17-18)
In a practical implementation of this SDR package, available processing power limits capability. Robin Gape discusses strategies for dealing with these limitations when using low-power hardware exemplified by the Raspberry Pi.

Data Transmission Through a Long Single-Wire Phone Line (19-24)
Brian Pease describes how he arrived at a simple solution for exchanging data and messages between distant underground camps and the surface using an existing phone wire.