The 4 port VoIP gateway is the smallest voice appliance in Telarvo’s SK VoIP Gateway range, and its job is to make a small voice deployment practical. Four channels, four SIM slots, and standard SIP registration cover a surprising range of use cases: a branch office with a handful of lines, a retail location that needs local numbers, a field team that carries a mobile trunk, or a business testing GSM-to-VoIP before committing to a larger chassis. Understanding what four ports do — and where the limits are — is the difference between a good small purchase and a premature upgrade.
This article covers what a 4-port gateway provides, which workloads it fits, and how it compares with the rest of the Telarvo VoIP range.
What Four Ports Provide
Four ports mean four GSM/LTE channels, each with a SIM card, and four simultaneous calls. The gateway registers with a PBX or softswitch over standard SIP, presents the four channels as a trunk, and terminates calls on the mobile network through the SIM lines. The same platform supports inbound and outbound calls, so the four channels carry both directions.
The 4-4 at $260.00 is Telarvo’s entry VoIP gateway. It is 2G/4G capable, supports multi-line GSM-to-VoIP conversion, and suits call centers, SMS services, and enterprise use — at a scale that matches four channels.
The Workloads That Fit Four Ports
The gateway fits workloads whose peak concurrency stays within four channels. A branch office with two or three simultaneous calls runs comfortably on a 4-4. A retail location that wants a local mobile number for customer calls uses one channel for inbound and has three left for outbound. A small field team can carry a 4-4 as a portable mobile trunk, registering it to the home PBX over a VPN.
The pattern is the same in each case: modest concurrency, local-number presence, and SIM-based termination. The 4-4 provides the mobile path, and the PBX provides the telephony logic. For a business that already runs a PBX and simply needs mobile lines, the 4-4 is the low-cost way to add them.
Integration with a PBX
The 4-4 registers with the PBX over standard SIP, so integration follows the usual trunk pattern: define a trunk that points at the gateway, assign each port a SIP identity, and route calls through it in the dial plan. Asterisk, FreePBX, and commercial IP-PBX platforms all work, because the gateway presents standard SIP rather than a proprietary interface.
Inbound calls from the SIM side arrive at the PBX as SIP calls and route to extensions or an IVR; outbound calls from the PBX terminate through the SIM lines. The main configuration work is number mapping — which SIM serves which route — and caller-ID presentation. Because the integration is standard, a 4-4 can be added to an existing PBX without special configuration, and the same setup scales to larger models when the workload grows.
Monitoring and Daily Operation
The monitoring rhythm for a 4-port gateway is small but real. The operations team checks call completion per channel, per-SIM volume, and registration status daily; reviews SIM balances weekly; and reconciles the carrier invoice monthly. The management interface shows the state of each module and SIM, so the review takes minutes.
The monitoring also produces the data for the upgrade decision. When per-SIM volume approaches operator terms or the busy-hour peak regularly brushes the four-channel ceiling, the 4-4 has reached its useful limit, and the measured numbers point to the next tier. The same SIP integration carries across the range, so the upgrade is a hardware swap rather than a re-integration.
A Worked Sizing Example
The following is a planning illustration with assumed values; confirm the numbers with your own call records. Assume a branch office places 200 calls per day and peaks at three simultaneous calls. Three channels cover the peak with one channel of headroom, and four numbers at 50 calls per day each are within typical operator terms. The 4-4 fits the workload.
If the same office grows to 500 calls per day and peaks at seven simultaneous calls, the measured numbers point to the 8-8 at $480.00. The example shows the method: the peak sets the channels, the volume per number sets the SIM count, and both are validated with measured data rather than assumed.
Security and Data Handling
The 4-4 is production infrastructure and should be secured accordingly. It sits behind the office firewall, the management interface is restricted, and SIP registration uses credentials. The local-first design keeps call records inside the business’s own network, subject to the SIM operators and any third-party services in use.
For a business with data-handling obligations, that control over where the call data lives is often the deciding factor between hardware and a hosted trunk. The gateway provides the control, and the business confirms the compliance side.
The Upgrade Path in the Range
The 4-4’s upgrade path is a practical benefit of the range. When the business outgrows four channels, the same SIP integration connects to an 8-8, a 16-port, or a 32-port model. The SIM cards move to the new chassis, and the trunk configuration carries over. The migration is a hardware swap plus a re-point, not a re-integration.
The upgrade decision follows the same measurement as the first purchase: the concurrent call peak and the volume per number. A business that tracks these numbers knows exactly when to move up, and the Telarvo range provides the step sizes without a platform change.
The Role of the Gateway in a Multi-Site Business
The 4-4 also has a place beyond a single office. A business with several small sites can run one 4-4 per site, each registering to the central PBX over a VPN, with local SIMs for local presence. The dial plan is centralized, the number mapping is per site, and caller-ID follows the local inventory. An office in one city calls through its local gateway and local numbers, while the central PBX routes overflow to other trunks.
The pattern suits businesses that want local numbers at each location without running separate PBX systems. The gateways register over standard SIP, and the SIM inventory at each site keeps the local numbers manageable. The 4-4 is the unit that makes the pattern affordable at branch scale.
The Cost Question
The 4-4’s cost is best evaluated against the workload it serves. At $260.00 with four SIM plans, the total depends on the plans as much as the hardware. For an operation placing 200 calls per day, the gateway pays for itself through local-number control and SIM-based termination; for an operation placing 20, the hardware may be idle.
The evaluation matches the tier to the measured workload, which keeps the purchase honest. The same method that sizes the first 4-4 sizes every upgrade, and the Telarvo range provides the step without a platform change.
Where the Limits Are
The limits follow the channel count. A workload that peaks at more than four simultaneous calls queues on a 4-4; a floor with 10 agents needs 10 channels, not four. The number inventory is the second limit: four SIMs provide four numbers, so an operation serving several markets with local presence outgrows the chassis quickly.
The useful ceiling is the point where the busy-hour peak approaches four channels or the SIM requirement exceeds four numbers. Beyond that, the 8-8 at $480.00 or a 16-port model is the next step, and the same SIP integration carries across the range.
Comparing with the 8-8
The choice between the 4-4 at $260.00 and the 8-8 at $480.00 is a concurrency question. If the peak fits four channels with headroom and growth is not expected soon, the 4-4 is the efficient purchase; the $220.00 difference buys four more channels and four more SIMs. If the business expects to add lines within a year, the 8-8 avoids an early upgrade.
The SIM side is separate from the channels. A 4-4 with a SIM bank or pool behind it can serve more numbers than four, because the gateway draws lines from the inventory rather than holding them in the chassis. The channel count and the number inventory are bought against different measurements.
Deploying a 4-4
Deployment follows the standard SIP trunk pattern. Connect the gateway to the network, register it with the PBX, insert the SIMs, and map the numbers. The dial plan routes calls to the gateway, and a test call through each channel confirms registration, audio, and caller-ID before production.
Because the integration is standard, a 4-4 can be added to an existing Asterisk, FreePBX, or commercial PBX without special configuration. The [VoIP Gateway collection](https://www.telarvostore.com/voip-gateway) lists the model with ports, SIM capacity, and price, and the same platform scales to larger models when the workload grows.
Frequently Asked Questions
What is a 4 port VoIP gateway?
It is a four-channel GSM-to-VoIP appliance with four SIM slots, registering with a PBX over SIP for mobile-number termination.
How much does the Telarvo 4-port gateway cost?
The SK VoIP Gateway 4-4 is listed at $260.00.
What workloads fit four channels?
Branch offices, retail locations, and field teams with peaks of up to four simultaneous calls, plus local-number presence.
Can a 4-4 use more than four numbers?
Yes, with a SIM bank or pool behind it — the gateway draws lines from the inventory, so the number count can exceed the chassis slots.
What are the upgrade options?
The same SIP integration connects to the 8-8, 16-port, and 32-port models when concurrency or number inventory grows.