The best replacement for pbx is voip.

The best alternatives to pbx are rated as following:
★★★★★  voip
★★★★  key system
★★★★  centrex
★★  ip pbx
★★  pabx
★  pstn
★  key
★  acd
★  sip
★  pri
★  key phone system
★  hosted
  pbx
  pots
  cbx
  ksu phone system
  ksu
  ip telephony
  kts
  ip centrex
  key telephone system
  switchboard
  ipbx
  private branch exchange
  voip phone system
  hosted voip
  key systems
  dwayne
  intercom
  avaya

Your alternative for pbx is not listed? Suggest!
Speaking about pbx, one probably shouldn't forget about voip.

Other search terms related to pbx and their ratings are:
★★★★★ voip
★★★ asterisk
You have in mind a companion for pbx and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of pbx in all years. Click on graph for more.
pbx
voip
key system