The hardware you need
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One of the most common questions from businesses considering an AI receptionist is what they need to buy. The honest answer is often nothing at all. If the AI answers calls in the cloud and your existing number simply forwards to it, the only hardware involved is whatever you already use to take calls today.

Things change when you want the AI to sit alongside your own phone system: answering first and passing calls to staff, sharing extensions, or taking calls from your operator's SIP trunk. This checklist covers what you need in that case, from the connection upwards.

First, decide where the AI sits

• Forwarding only. Your existing line forwards some or all calls to an AI number. No new hardware. Your operator sets up the forwarding, often with a short code on the line itself.
• AI in front of your phone system. Calls reach the AI first, which answers routine requests and passes others to staff on desk phones or a phone system. You need a working IP phone system and a reliable network.
• SIP trunk into the AI. Your operator's SIP trunk, or your phone system, sends calls straight to the AI platform over the internet. You need the network items below and your operator's agreement. See our SIP trunking guide.

1. An internet connection with headroom

Voice over IP is not demanding in raw bandwidth, but it is demanding in consistency. Cisco's calculation for the standard telephone codec, G.711, comes to 87.2 kbps per call in each direction over Ethernet, once packet headers are included. Ten simultaneous calls therefore need under 1 Mbps each way, which almost any business connection can provide.

What matters more is delay, jitter and packet loss. Cisco's long-standing design targets for voice are one-way delay of no more than 150 ms, average jitter under 30 ms and packet loss no higher than 1%, and well-run networks aim for close to zero loss. A connection that is fast on a speed test can still be poor for voice if it is congested, shared with large uploads or prone to drop-outs.

Checklist:

• A business-grade line, with a second connection or 4G/5G failover if phones are critical.
• Upload capacity that is not saturated by backups, cloud sync or video at busy times.
• A wired connection for desk phones and any on-site phone system. Avoid putting a PBX on Wi-Fi.

2. A router configured for voice

Most "phantom" phone problems, such as one-way audio, calls that drop after a fixed time, or phones that stop ringing, trace back to the router.

• Turn off SIP ALG. Many routers ship with a "SIP application layer gateway" that rewrites call signalling. 3CX strongly recommends using a router without SIP ALG or one where it can be fully disabled, warning that it will in most cases break the SIP exchange. Some routers re-enable it after a restart, so check again after firmware updates.
• Keep NAT mappings stable. Make sure the firewall does not keep changing the ports it uses for voice traffic, and that UDP timeouts are long enough for calls to stay connected.
• Allow your provider's addresses. If you use a SIP trunk, allow its signalling and media IP ranges on the firewall. A firewall blocking incoming audio is one of the most common causes of one-way audio.
• Prioritise voice. Use quality of service to mark voice packets as Expedited Forwarding (DSCP 46), the class recommended for telephony in IETF guidance, and give them priority over bulk traffic.

3. A phone system (PBX), if you need one

A private branch exchange routes calls between your lines and your staff: ring groups, extensions, transfers, voicemail. Options include:

• Cloud or hosted PBX. No box on site; your phones register to a service over the internet. Usually the simplest choice for small businesses.
• Software PBX. Products such as 3CX, or open-source Asterisk with the FreePBX interface, run on your own server or in the cloud and connect to SIP trunks from your operator.
• Your operator's managed service. Many operators offer a managed business voice or unified communications package that includes the PBX.

For an AI receptionist in front of your team, the PBX needs to be able to receive calls from, and send calls to, the AI platform over SIP. Ask your provider whether that is supported and how transfers are signalled.

4. Phones and headsets for your team

• IP desk phones. Standards-based SIP phones from makers such as Yealink, Poly and Grandstream work with most phone systems. Look for Power over Ethernet so a single cable carries data and power; standard PoE supplies up to 15.4 W at the switch port, enough for typical desk phones.
• DECT cordless. For staff who move around a shop floor or building, a DECT base station connects to the phone system and supports several cordless handsets or headsets.
• Softphones. An app on a computer or mobile can replace a desk phone entirely.
• Headsets. For staff who take many calls, a headset is worth it. Check how it connects to the phone (USB, Bluetooth, an RJ9 headset port, or an electronic hook switch cable that lets a wireless headset answer calls).

The AI itself needs none of this. Phones are for the people the AI hands calls to.

5. Gateways for analogue equipment

Older equipment does not disappear just because the phone line goes digital.

• Analogue telephone adapters (ATA) with FXS ports connect ordinary analogue phones, fax machines, door entry phones or lift lines to an IP phone system.
• FXO gateways go the other way, connecting an IP system to analogue lines. Some businesses keep one as a fallback in case the SIP trunk fails.

Audit what is plugged into your current lines before you change anything: alarms, payment terminals, lift emergency phones and door entry systems are easily forgotten. In the UK this is urgent because of the analogue switch-off; see our UK guide.

6. Switches and power

• A network switch with PoE for desk phones and DECT bases.
• A separate voice VLAN, if your network is large enough to warrant it, to keep phone traffic apart from computers.
• An uninterruptible power supply for the router, switch and any on-site PBX, so phones keep working through a short power cut.

The short version