Grandstream UCM6304A Audio Series IP PBX – 4 FXS/FXO Ports, 1000-User Capacity & Advanced Audio Conferencing
Medium-sized businesses often need a phone system that bridges legacy analog phones and PSTN lines with modern VoIP calling, conferencing, and remote work tools—without unnecessary complexity or cost. The Grandstream UCM6304A Audio Series IP PBX does exactly that in one compact, reliable appliance. It supports up to 1,000 users and 150 concurrent calls while providing 4 FXS ports for analog phones and 4 FXO ports for direct PSTN connectivity, complete with lifeline failover during power outages.
Built on Asterisk 16, it includes a full unified communications platform with instant messaging, high-quality audio conferencing, and the free Wave app that lets teams collaborate from desktops, web browsers, or mobile devices. Advanced security features, easy ZeroConfig provisioning for Grandstream endpoints, and cloud management options through GDMS or UCM RemoteConnect make day-to-day operations smoother for IT teams and business owners alike.
The Telecom Spot Take
For many of our customers running 50–300+ person operations, the UCM6304A hits the sweet spot between capability and simplicity. The four FXS/FXO ports give you a clean migration path—you keep the analog phones and lines you already have while adding IP endpoints and remote users. The 1,000-user / 150-call capacity provides real headroom without jumping to a larger chassis, and the integrated conferencing plus Wave app reduce the need for separate meeting or softphone subscriptions.
What stands out in real deployments is the combination of Full-Band Opus audio quality, strong jitter resilience, and layered security (SRTP, TLS, STIR/SHAKEN, Fail2Ban). It’s straightforward to manage locally or through Grandstream’s cloud tools, which matters when you want reliable performance without constant IT babysitting. If your business needs dependable voice infrastructure that supports both in-office and hybrid teams, this model earns its place as a practical, future-ready choice.
Key Features
- Hybrid Analog + IP Connectivity — Connect up to 4 analog phones (FXS) and 4 PSTN lines (FXO) directly. Lifeline capability automatically routes calls during power outages so critical communications stay up.
- Room to Grow — Supports 1,000 users and 150 concurrent calls (120 with SRTP encryption), giving medium businesses breathing room as teams expand.
- Clear Audio on Any Network — Full-Band Opus codec plus advanced processing (NetEQ, FEC 2.0, dynamic jitter buffer) delivers crisp voice even when networks are congested or have up to 50% packet loss.
- Built-in Collaboration Platform — Host voice and web meetings across up to 7 rooms with a combined 120 participants. No extra licensing required for core audio/web conferencing.
- Remote Work Without the Headaches — The free Wave app (desktop, web, Android/iOS) lets employees make/receive calls, join meetings, send IMs, and share files from anywhere. UCM RemoteConnect provides secure, reliable NAT traversal.
- Efficient Call Handling — Advanced call queues with virtual callback, ring groups, IVR, follow-me, and full call center statistics help route calls faster and improve customer experience.
- Enterprise-Grade Security — SRTP/TLS encryption, secure boot, unique certificates, random default passwords, firewall with Fail2Ban, and STIR/SHAKEN caller ID authentication protect calls and data.
- Simple Deployment & Management — ZeroConfig auto-provisions Grandstream phones, while the web GUI, GDMS cloud monitoring, and API integrations (CRM/PMS) keep everything manageable for IT teams or business owners.
Technical SpecificationsCategoryDetailsMax Users1,000Concurrent Calls150 (G.711) / 120 with SRTP encryptionMeeting CapacityUp to 7 simultaneous public rooms; max 120 participants across all roomsAnalog Ports4 FXS (analog phones) + 4 FXO (PSTN lines); lifeline failover on allNetwork Interfaces3 × self-adaptive Gigabit Ethernet (switched / routed / dual mode) with PoE+Peripheral Ports2 × USB 3.0, 1 × SD card slotVoice Codecs & QualityOpus (Full-Band), G.711 A/U-law, G.722, G.722.1/1C, G.723.1, G.726-32, G.729A/B, iLBC, GSM; T.38 fax; advanced LEC, NetEQ, FEC 2.0, jitter resilience up to 50%SecuritySRTP, TLS 1.2, HTTPS, SSH, 802.1X, secure boot, unique certificate, random passwords, Fail2Ban, firewall, STIR/SHAKENRemote & CollaborationFree Wave app (Win/Mac, Chrome/Firefox, Android/iOS); UCM RemoteConnect; built-in IM & web meetingsManagementWeb GUI, ZeroConfig provisioning, GDMS cloud management, full API for CRM/PMS integrationPowerDC 12V input; 100–240 VAC, 50/60 Hz adapter (1.5 A)Dimensions & Weight270 mm (L) × 175 mm (W) × 36 mm (H); unit ≈ 775 gComparison at a Glance
The UCM6304A sits in the ideal middle of the UCM6300 Audio Series for growing medium businesses:
- vs UCM6302A — Doubles analog ports (4 FXS/4 FXO vs 2/2) and user capacity (1,000 vs 500), with higher concurrent calls (150 vs 75) and more meeting participants (120 vs 75). Better when you have more legacy equipment or expect growth.
- vs UCM6308A — Same three Gigabit ports with PoE+, same strong codecs and security, but with fewer analog ports (4 vs 8) and lower max capacity (1,000 users/150 calls vs 1,500/200). Choose the 6304A when you don’t yet need the extra scale or port density of the larger model.
- Audio-focuséd design: Choose the UCM6304A when your priority is clear voice, messaging, and audio conferencing without the added complexity or cost of video conferencing hardware found in the standard UCM6300 series.
All models share the same core platform (Asterisk 16, Wave app, RemoteConnect, GDMS, advanced voice processing), so you get consistent quality and management across the lineup.
FAQ
How many users and simultaneous calls does the UCM6304A support?
It supports up to 1,000 users and 150 concurrent calls (120 when using SRTP encryption). This gives medium businesses comfortable headroom for growth.
Can I keep my existing analog phones and PSTN lines?
Yes. The UCM6304A includes 4 FXS ports for analog telephones and 4 FXO ports for direct PSTN lines. All ports have lifeline capability that automatically maintains connectivity during power outages.
What remote collaboration tools are included?
The free Wave app works on Windows, Mac, web browsers (Chrome/Firefox), Android, and iOS. It supports voice calls, instant messaging, file sharing, and joining or hosting meetings. UCM RemoteConnect provides secure, reliable access without complex VPN setups.
Does it support high availability or redundancy?
Yes. The UCM6304A supports Hot Standby High Availability (HA) for failover between two units, helping protect business continuity.
How secure is the system for remote workers and sensitive calls?
It includes multiple layers: SRTP and TLS encryption, secure boot with unique certificates, random default passwords, firewall rules, Fail2Ban, and STIR/SHAKEN caller ID authentication to help combat spoofing and fraud.
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Additional Information: Unless otherwise stated in description, returns are accepted within 30 days from date of invoice. A RMA number must be requested before returning any tiems. Merchandise must be in its original condition, unopened and unuséd. Sales on software and licenses are final and not eligible for refund. Buyer is responsible for return shipping, and all returns are subjected to a 20% restocking fee. If the RMA procedures are not followed we may in our sole discretion reject the entire return or choose to impose additional charges against the customer for replacement of the missing item(s). Refunds will be given as merchandise credit. integration by
