Cisco VIC3-4FXS/DID
Four-Port Voice Interface Card - FXS and DID
Product Highlights
Integrating legacy analog telephony equipment into a modern IP network shouldn't require a forklift upgrade. The Cisco VIC3-4FXS/DID Four-Port Voice Interface Card bridges the gap between traditional analog devices and your Cisco Unified Communications infrastructure, letting you preserve investments in phones, fax machines, and key systems while migrating to VoIP.
This 3rd-generation voice interface card provides four RJ-11 ports, each independently configurable as either a Foreign Exchange Station (FXS) interface or a Direct Inward Dialing (DID) trunk interface. In FXS mode, the card supplies dial tone, ringing voltage, and battery feed to connected analog endpoints. In DID mode, it accepts incoming calls from a central office, enabling direct routing to internal extensions without an attendant.
Designed as a plug-in module for Cisco Integrated Services Routers, the VIC3-4FXS/DID installs into VIC or WIC slots on Cisco 2800, 2900, 3800, and 3900 series platforms — or into compatible voice network modules such as the NM-HD-1V and NM-HD-2V. It requires a PVDM DSP module on the host router and a Cisco IOS IP Voice feature set, ensuring enterprise-grade voice quality with support for industry-standard codecs. Whether you're extending analog service to a branch office or consolidating DID trunks at a campus edge, the VIC3-4FXS/DID delivers reliable, cost-effective analog connectivity.
Features & Benefits
Flexible FXS & DID Operation
Each of the four ports can be configured as either an FXS interface — providing dial tone, ringing voltage, and caller ID to analog phones and fax machines — or as a DID trunk interface for receiving inbound calls from the PSTN. This dual-mode flexibility lets you tailor the card to your exact deployment needs on a per-port basis.
Broad Router Platform Compatibility
The VIC3-4FXS/DID is supported on Cisco 2800 series (2801, 2811, 2821, 2851), Cisco 3800 series (3825, 3845), and Cisco 2900/3900 series ISR G2 routers. It can be installed directly into on-board VIC/WIC slots or into voice network modules like the NM-HD-1V, NM-HD-2V, NM-HD-2VE, and NM-HDV2, giving you deployment flexibility across your router fleet.
Enterprise Voice Signaling
The card supports loop-start and ground-start signaling in FXS mode, and Immediate, Delay-dial, and Wink-Start signaling in DID mode. In-band DTMF and out-of-band pulse dialing (8–12 pps) are both supported, ensuring interoperability with a wide range of PBX systems and central office equipment.
International Ringing & Caller ID
Configurable ringing frequencies (20, 25, 30, and 50 Hz) and ringing voltage of 45 Vrms make the VIC3-4FXS/DID suitable for deployments worldwide. In FXS mode, the card generates battery polarity reversal and caller ID, supporting both FSK and DTMF caller ID formats.
Cisco IOS Integration
Fully managed through the Cisco IOS command-line interface, the VIC3-4FXS/DID integrates with dial-peer configurations, voice-class codec settings, and Cisco Unified Communications Manager (CUCM) or Cisco Unified Communications Manager Express (CME). Firmware updates are delivered as part of standard Cisco IOS upgrades — no separate card firmware to manage.
Deployment Scenarios
Branch Office Analog Phone Extension
Deploy the VIC3-4FXS/DID in a branch-office Cisco ISR to connect existing analog phones and fax machines to a centralized IP PBX. Each FXS port delivers dial tone and ringing to local endpoints, preserving legacy equipment while enabling unified dial-plan management from headquarters.
DID Trunk Termination for Small/Medium Business
Configure the card's ports in DID mode to terminate inbound DID trunks from a local central office. This allows external callers to reach internal extensions directly, eliminating the need for a receptionist or auto-attendant on incoming DID calls.
Mixed FXS/DID Deployment in Retail or Hospitality
Use a combination of FXS and DID ports on a single card to simultaneously connect analog lobby phones, back-office fax machines, and an inbound DID trunk — all through one Cisco ISR, reducing hardware footprint and simplifying management at each site.
General
Interfaces
Signaling
Electrical
Software
Compliance & Safety
Compatibility Notes
Supported Router Platforms
- Cisco 2800 Series: 2801, 2811, 2821, 2851
- Cisco 3800 Series: 3825, 3845
- Cisco 2900 Series (ISR G2): 2901, 2911, 2921, 2951
- Cisco 3900 Series (ISR G2): 3925, 3945
Installation Slots
- On-board VIC/WIC slots on supported routers
- Voice network modules: NM-HD-1V, NM-HD-2V, NM-HD-2VE, NM-HDV2
Software Requirements
- Minimum Cisco IOS: Release 12.4(15)XZ or 12.4(20)T (for Cisco 2800/3800 series)
- Feature Set: Cisco IOS IP Voice (IPVOICE) feature set required
- DID mode on Cisco 2811/2821/2851/3825/3845 requires Cisco IOS 12.3(14)T or later
DSP Requirements
- One or more PVDM2 or PVDM3 DSP modules must be installed on the host router when the VIC is placed in a chassis WIC slot. If installed in a voice network module, the module itself must contain DSPs.
Cabling
- Standard straight-through RJ-11 modular telephone cables
Downloads & Resources
Frequently Asked Questions
| Part Number | Product | Key Difference |
|---|---|---|
| VIC3-2FXS/DID | Cisco 2-Port FXS/DID Voice Interface Card | 2-port version — ideal when fewer analog ports are needed, freeing budget and slot density for other modules. |
| VIC2-4FXO | Cisco 4-Port FXO Voice Interface Card | Provides 4 FXO ports for connecting to PSTN/CO lines (accepts line voltage), whereas the VIC3-4FXS/DID provides FXS ports (supplies line voltage to endpoints). |
| NIM-4FXS | Cisco 4-Port FXS NIM for ISR 4000 | Next-generation NIM form factor for Cisco 4000 Series ISRs — the successor to the VIC3-4FXS/DID for ISR 4300/4400 platforms. |
| VIC3-2FXS-E/DID | Cisco 2-Port FXS-E/DID Voice Interface Card | Enhanced 2-port FXS variant with extended loop length support — choose when longer cable runs to analog endpoints are required. |
