Business telephony has moved to IP: with the gradual shutdown of the traditional telephone network (PSTN), VoIP has become the standard. But between SIP, IPBX, IP phones, trunks, and cloud telephony, the terminology can be overwhelming. This guide clarifies the concepts and helps you equip your business without mistakes.
VoIP, ToIP, SIP, IPBX: clear terminology
- VoIP (Voice over IP): transmitting voice over the computer network instead of a traditional phone line.
- ToIP (Telephony over IP): the entire telephone system based on IP.
- SIP: the standard protocol that establishes calls. A SIP trunk is the link provided by the operator to make/receive calls.
- IPBX: the next-generation “telephone switchboard” that manages extensions, transfers, voicemail, IVR…
How IP telephony works
IP phones connect to the network (like a computer) and register with the IPBX. The IPBX links extensions together and to the operator’s SIP trunk. The result: a single network for data and voice, centralized management, and great flexibility (adding extensions, numbers, remote work).
On-premise IPBX or cloud telephony?
Two approaches: on-premise IPBX (equipment hosted on your premises—control and independence) or cloud telephony / Centrex (the IPBX is hosted by the operator—subscription, zero maintenance). On-premise remains relevant for those who want to keep control and amortize an investment, especially with tested second-hand equipment.
Choosing your IP phones
- Entry-level phones: for everyday use (reception, offices).
- Advanced phones: large color screen, programmable keys, for managers and receptionists.
- IP DECT: cordless handsets for mobility within the premises.
- Conference phones: for meeting rooms.
- Headsets: essential in call centers or open offices.
The role of the network: PoE, QoS, voice VLAN
Good IP telephony relies on a well-designed network. PoE powers phones via the Ethernet cable (see our PoE guide). QoS and a dedicated prioritized voice VLAN prevent dropouts and choppy voice—hence the importance of a managed switch on the network.
Which brands?
Two solid references: Yealink, widely used for its IP phones offering good value and compatibility with most IPBXs/SIP operators, and Avaya, a trusted name in enterprise telephony systems. Find them all in our professional VoIP and IPBX phones collection.
Used VoIP equipment
Tested used IP phones, IPBXs, and gateways allow you to equip an entire business at a fraction of the new price, with reliable professional equipment. Each device is checked and guaranteed. For general context, see our used IT equipment guide.
FAQ: business telephony
What is the difference between VoIP and SIP?
VoIP is the concept (voice over IP); SIP is the protocol that establishes and manages calls. The SIP trunk is the operator’s service to make and receive calls.
Should I choose an on-premise or cloud IPBX?
Cloud avoids maintenance via a subscription; on-premise offers more control and amortizes investment, especially with used equipment. The choice depends on your size and management preferences.
Does an IP phone work with any operator?
Most standard SIP phones are compatible with a wide range of IPBXs and operators. However, check the announced SIP compatibility and provisioning.
Why is my voice choppy on VoIP?
Often a network issue: no QoS, no voice VLAN, or insufficient bandwidth. A managed switch with QoS and a dedicated VLAN usually fixes the problem.
In summary
Equipping your business telephony means choosing between on-premise and cloud IPBX, selecting IP phones suited to your needs, and optimizing the network (PoE, QoS, voice VLAN). With tested used VoIP equipment, you get reliable professional solutions at a controlled cost.