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# format auto-updated on access: Mon 27-Nov-2017 11:29:56 +01:00 CREG Journal Contents. (This is a bit-map scan). Update Flashgun slave, VLF licensing. Practical Earth Return Telephone Design In part 2, Nigel Lovell presents constructional details of the unit introduced in the last issue. Inductaphones and Conductaphones Steve Clark summarises the three systems of cave communication he has experimented with. Theoretical Considerations for a Low Noise Pre-amp Comment on David Gibson's article by Derek Potter. Earth Current Communications Comment on Nigel Lovell's article by Derek Potter. Designing a Low-noise Receiver Pre-amp David Gibson summarises the signal/noise and reception range equations and gives some worked examples. Flashgun Slaves for Flashbulbs David Gibson gives a circuit for adapting slave units to work with bulbs, and Steve Clark gives a design for a slave unit. Introduction to Radio Location In the final instalment of our series for those new to cave communication, Mike Bedford brings radio location under the spotlight. FX2s and PVC Drain Pipe Nigel Lovell describes the construction of a low cost FX2 style lamp. Penetration of Magnetic Fields Underground In this, the third part of our 'optimum frequency' series, David Gibson derives graphs of s/n ratio against frequency for various rock conductivities. Expected Values of Atmospheric Radio Noise John Rabson presents the figures, and David Gibson gives some guidance on how to use them.