🚀 go-pugleaf

You can make sound-powered telepones from "piezoelectric speaker 
elements" available at Irish Electronics (Ray D. O'Shack :-), part # 
273-091 ($2.49).  Just connect one to each end of a pair of wires.  
It's a great toy for kids, and may have "real" applications too.

Speech is fully intelligible despite a jagged frequency-response 
containing many resonances.  The device is manufactured by MuRata of 
Japan.  

These devices are compatible with U.S. Army TA-1/PT sound-powered 
field telephones.  They are also the same diameter as the microphone 
in the TA-1, and can be used as a field-expedient replacement. 
Humidity tolerance and range have not been determined.  The TA-1's 
electromagnetic transducers are somewhat delicate and will break 
internally if subjected to mechanical shock (like dropping the phone 
on a hard surface).

--

Frank Reid     W9MKV     reid@ucs.indiana.edu