Cisco 4-Port High-Density FXS/DID Analog Voice Interface
Card for the Cisco 1700 Series Modular Access Routers

The Cisco 1700 Modular Access Router is designed to provide a cost-effective integrated access platform for small and medium-sized businesses and small enterprise branch offices. It supports advanced services e-Business features such as VPNs; secure Internet, intranet, and extranet access with optional firewall technology; broadband DSL and cable connectivity; and multiservice voice/video/data/fax integration.

Figure 1

Cisco 4-Port FXS/DID VIC with Caller ID Support in FXS mode


The 4-port high-density FXS/DID VIC1 can support up to 4 foreign-exchange-station (FXS) ports for directly connecting phones or fax machines, or it can be used to connect up to four direct-inward-dial (DID) analog trunks, providing customers the flexibility they need for their unique business environment (refer to Figure 1). Each port on the 4-Port FXS/DID VIC is selectable for use in either FXS or DID mode when using phones with 1 REN þload or less2 . The 4-Port FXS/DID VIC is the same size as the existing two-port voice interface cards (VICs), allowing it to slide into either WIC/VIC slot or VIC slot in Cisco 1751 and 1760. The Cisco 1751 can support three VIC-4FXS/DID cards with a maximum of four ports in DID mode. The Cisco 1760 can support four VIC-4FXS/DID cards with a maximum of eight ports in DID mode. Figure 2 shows a typical application of 4-port VIC-FXS/DID in a small enterprise branch office with KTS or small PBX. The VIC-4FXS/DID in the Cisco 1700 is used to connect analog phones or fax machines. The long-distance calls between small enterprise branch offices and headquarters are carried by IP network, while the local calls are carried by PSTN, which also provide backup to the IP network.

DSP Requirements for the Cisco VIC-4FXS/DID

For Cisco 1751 and 1760 routers, the medium-complexity analog digital-signal-processor (DSP) image is the factory default for supporting the 4-Port FXS/DID VIC. This DSP image provides support for four voice channels (of G.711, G.729a, or G.726) for each DSP chip. For example, the Cisco PVDM-256K-4 DSP Module has one DSP chip and is, therefore, capable of supporting four voice channels on the 4-Port FXS/DID VIC. The medium-complexity analog DSP software image supports four channels of G.711, G.729a, G.726, fax relay, or modem or fax pass-through, and it provides support for 32-msec echo cancellation per DSP chip.

Figure 2

Small Offices with POTS Phones and Fax Machines

The 4-Port FXS/DID VIC also support the high-complexity analog DSP software image. This DSP image provides support for two voice channels (of G.711, G.729, G.723.1, G.728, or G.726) for each DSP chip. Therefore, a Cisco PVDM-256K-8 Module (two DSP chips) is required to support four voice channels on the 4-Port FXS/DID VIC. The high-complexity analog DSP image supports two channels of G.711, G.729, G.726, G.728, G.723.1, fax relay, or modem or fax pass-through, and it provides support for 32-msec echo cancellation per DSP chip.

For DSP requirements on the Cisco 1751 and 1760 routers with Cisco IOS® 12.2(8)YN or later releases, refer to the DSP Calculator at the following URL:

Key Benefits and Technical Specifications

Table 1 provides the benefits and specifications and Table 2 provides the Electro Magnetic Compatibility (EMC) standards for the 4-Port FXS/DID VIC.

Table 1  Benefits and Specifications of the Cisco 4-Port FXS/DID VIC

Part Number: VIC-4FXS/DID

4-port FXS or DID voice/fax interface card with caller ID support in FXS mode only (DID for United States, Canada, and other countries)

Interface type

FXS and DID trunk

Supported platforms

Cisco 1751 and Cisco 1760

First Cisco IOS® Release

Cisco IOS 12.2(8)YN (this is a short lived Early Deployment (ED) release which will merge into IOS 12.3(1)T)

Minimum Feature Sets


Ringer Equivalence Number (REN)

A maximum of five REN loads can be supported on each voice port

A maximum of eight REN loads can be supported on each 4-port FXS/DID VIC

A maximum of twenty REN loads can be supported on each Cisco 1751 and 1760 router


UL 60950 (United States), CSA C22.2 No. 60950-00 (Canada), EN 60950 (Europe), AS 3260 (Australia), TS 001 (Australia))

FXS homologation

United States (TIA/EIA-1S-968), Canada (CS-03 I)

DID homologation

United States (TIA/EIA-1S-968), Australia (ACIF S002/S003)


Refer to Table 2


Part number VIC-4FXS/DID=

Signaling modes

FXS—Loop Start

DID—Wink, Immediate, and Delay Dial

Address Signaling formats

In-band dual tone multifrequency (DTMF)

Out-of-band pulse (10/20 pps)

Tone disconnect supervision

DID—Power denial (caller party control, far-end disconnect)

Ringing frequencies

20 Hz, 50 Hz

Physical connector


Number of connectors


Mean time between failure (MTBF)

2,131,306 hours

Table 2  EMC for the Cisco 4-Port FXS/DID VIC

FCC Part 15 Class B


EN55022: 1998, Class B


EN61000-3-2: 1995


EN61000-3-3: 1995


EN50082-1: 1997


EN55024: 1998









RF fields






Conducted RF


Voltage dips/sags/interruptions

1 VIC-4FXS/DID will not be able to register with Cisco CallManager currently.
2 If the REN load on any FXS port is greater than 1 REN, all four ports of a single VIC-4FXS/DID card must be configured as FXS; The mix of DID and FXS is not allowed in this case.
2007/05/04 11:34 2007/05/04 11:34

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