- Polymer-bonded explosive
- Pre-B-cell leukemia homeobox
- Private branch exchange, a telephone exchange
that services a particular business or office
That led to more questions, but I think #3
tells me the answer I was seeking – Private Branch Exchange
The term PBX was first applied when Switchboard Operators ran company switchboards by hand. As automated electromechanical and then electronic switching systems gradually began to replace the manual systems, the terms PABX (private automatic branch exchange) and PMBX (private manual branch exchange) were used to differentiate them. Now, the term PBX is by far the most widely recognized. The acronym is now applied to all types of complex, in-house telephony switching systems.
