That was a REAL telephone :-)

[Bob Bruhns]

It's interesting how much analog technology went into the design of a 
phone even back then, and for years before that.  Partial hybrid balance 
to control sidetone volume, line length compensation to boost talk 
output on longer lines, all done with passive analog circuitry.  The 
weakest link was the carbon element in the microphone.  Fabulous high 
output, but eventually the carbon would compress or something, and that 
sounded terrible.  When that happened, I would rap the mike on the 
table, and it would be good again for a while.

The first touch-tone phones were sensitive to line polarity.  If the DC 
polarity was backwards, everything worked, except that the touch tone 
pad would not generate tones.  Nowadays the phones have a bridge 
rectifier on the line connection, so polarity doesn't matter.

    Bob, WA3WDR