What capability did the quadruplex telegraph introduce to the telegraph infrastructure?

Answer

Sending four messages simultaneously over a single wire

The quadruplex telegraph represented a significant advancement in communication efficiency. By allowing two messages to be sent in each direction simultaneously on one wire, the technology effectively quadrupled the capacity of existing infrastructure. This innovation greatly increased the revenue potential for telegraph companies without the need for the significant expense of installing new physical wiring.

What capability did the quadruplex telegraph introduce to the telegraph infrastructure?
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