Grandstream UCM6304 IP PBX

The Grandstream UCM6304 is the mid-to-large on-site PBX of the UCM6300 range: up to 2,000 users and 300 concurrent calls, with four FXS and four FXO ports built in.

Four of each is the point of difference. A site with a lift phone, an alarm dialler, a fax and a door entry panel needs four FXS ports — and often has two or three analogue exchange lines to keep alongside them. The 6304 absorbs all of that without a separate gateway.

If you encrypt call media, note the honest number: 300 calls in the clear, 200 with SRTP. Encryption costs processing, and it is better to know that before the busiest morning of the year.

Key features

• Up to 2,000 users — registered SIP endpoints
• 300 concurrent calls, or 200 with SRTP encryption
• 4 FXS and 4 FXO ports — four analogue devices and four analogue lines
• Lifeline on the analogue ports — an analogue phone still works in a power cut
• Gigabit networking — router or switch mode
• Full PBX features — voicemail, IVR, call queues, ring groups, call recording
• Wave app — desktop, mobile and web softphone included
• Video and audio meetings — hosted on the PBX itself
• Expandable with gateways — add analogue capacity with a GXW or HT gateway
• No per-seat licence for core telephony

Works with

• UCM6301 — 500 users, 75 calls, 1 FXS + 1 FXO
• UCM6302 — 1000 users, 150 calls, 2 FXS + 2 FXO
• UCM6308 — 3000 users, 450 calls, 8 FXS + 8 FXO
• Grandstream GRP desk phones — zero-touch provisioning from the UCM
• Grandstream DECT cordless — register handsets to the same system
• GXW4248 V2 — add 48 analogue extensions

Frequently asked questions

2,000 users but 300 calls — which number matters?

Concurrent calls, almost always. Size on the busiest ten minutes of your week rather than on headcount; user count is rarely the limit anyone hits.

Why does SRTP reduce the call count?

Encrypting and decrypting media in real time takes processing power, so the ceiling drops from 300 to 200. If everything is encrypted end to end, plan against 200.

What is the difference between FXS and FXO?

FXO takes a line in — plug an analogue exchange line into it. FXS gives a line out — plug an analogue phone, fax or door phone into it. The UCM6304 has four of each.

6304 or 6308?

Analogue ports and call ceiling. Four of each and 300 calls suits most larger offices; go to the 6308 when you need eight analogue ports or more than 300 simultaneous calls.

Do I still need a SIP provider?

Yes — the UCM is the phone system, not the phone lines. It connects to your SIP trunk provider, or to analogue lines through the FXO ports, or both.

Is there a licence cost?

Not for core telephony — users, calls, voicemail, IVR and queues are included. Optional extras such as UCM Remote Connect for VPN-free remote working are separate subscriptions.

Sizing a phone system? Call 0333 242 1314 or email sales@clisecure.com — tell us the staff count, the busiest hour and how many analogue devices there are, and we will size it properly.