For the impatient:
Our main contributor is a field telephone aficionado, and we compiled the most comprehensive comparison of field telephones ever made.
If you’re happy with your field telephone, you don’t need a new one, they never break — it’s as simple as that. If you’re having problems with range, or reliability, though, it might be time for an upgrade. Also if you never had one and plan to acquire your first ever field telephone we cover your needs.
Our main criteria were weight, sturdiness, reliability and also availability on the market. A good field telephone should be lightweight but heavy duty and use very reliable technology, it should be prepared to take a beating.
US made TA-1/PT, a sound powered lightweight (1.3kg) device. It is not waterproof (not submergible) but very weatherproof and heavy duty. It should survive the harshest conditions. It is specified for an attenuation margin of 10dB which can yield up to 10km speaking and signalling distance on a good field wire. The device includes a signalling generator and an adjustable buzzer (loud to off) and a visual call indicator. Being sound powered no batteries required. It is available from army surplus stores and on ebay for 50 to 100 US$/Euro.
If you require longer communication distance or a waterproof device then look no further than the Norwegian TP-6N. Being a powered device its specified attenuation margin is 35dB enabling speaking and signalling distances of up to 35km. The device is still lightweight with 1.8kg and it is waterproof (submergible, at least for a short time, according to this it is very popular for cave rescue communication). It is operated with three 1,5V standard D-Cells which last for about 3 months with typical usage. The drawback of this device are it's guts which use a transistorised circuit, if it fails then it is less repairable than the electromechanical technology on typical field telephones. Supply from surplus stores seem to run out, typical prices are now >100 US$/Euro, but you might still find one for less on ebay from time to time.
The Swedish M/37 and it's later derivates have been (and are still) in worldwide use. It is bigger and with 4.2kg more than twice as heavy as our main picks. The bakelite case is not too crash resistant and it is also not waterproof but still reasonably weatherproof. But in comparison to the main picks it is much more suited to be operated as a desk phone (some models even include a dial for connection to an automatic network, it should support pulse dialling) if that suits your planned use. It is operated with two standard 1,5V D-Cells and will operate on line lengths of at least 15 to 20km without issues. The big advantage is the price, it can be had for less than 25 US$/Euro from surplus or ebay, often with optional dial and an additional headset included.
Other instruments we consider good alternative choices are the Swiss FTf 50 (2.6kg, single 1,5V D-Cell, harder to find than our picks) the German Bundeswehr FF OB/ZB (4.3kg, 2x 1,5V D, ~25US$/Euro from surplus) or the US TA-312/PT (4.3kg, 2x 1,5V D, waterproof, ~100US$/Euro from surplus). The oldest instrument we recommend is the US EE-8 (5.3kg, 2x 1,5V D, very heavy duty and easy to repair, can be found for less than 50US$/Euro from surplus in very nice conditions).
Also to be found very cheap are east European and USSR instruments. The disadvantage is that these often use special battery sizes. A device we still can recommend is the Czech TP-25 (3.8kg, 1x 1,5V, very nice finish and quality, often to be found for less than 25 US$/Euro), the battery compartment is prepared to take a field element of size S4 (57x57x115mm), more than enough space for almost any modern 1,5V battery, also some already come with an adapter for a D-cell.
The advantage of the simple analog local battery technology is that pretty much any field telephone you will find will still operate or be easy to fix and will interoperate with any other (also sound powered and local battery devices can interoperate). Have a look on your grandpas or neighbours attic.
Anything pre 1930, it will be heavy but not very heavy duty (e.g. wood frames) and most are collectors items, leave them to collectors, or become one :-).
This guide is not meant to be taken too serious, but we stand by our recommendations.
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