[GreenKeys] The "Low Down" on Bell Ringers

[Jim Haynes]

Then there was the technique we called "bell break"  Used a switch
actuated by the bell, mainly because it has a convenient mechanism to
operate a switch.  The switch operated a special relay which was of a
flip-flop nature; it reversed position on successive pulses to the
winding.  This was used to control the transmit-receive switch.

To use it, two stations would engage the feature while one was 
transmitting and the other was receiving.  Then when the transmitting
guy wanted to turn the circuit over to the receiving guy he would
just send bell and that would reverse the transmit-receive condition
at both stations.  And the bell called attention to the fact that this
had happened.

Definitely not compatible with "bell ringers"