---

title: "IDM NTD421 Multi-Service Telephone Optical Terminal"
model: "IDM NTD421"
category: "Telephone Optical Terminal"
tags:

• "Multi-Service Optical Terminal"
• "Telephone Media Converter"
• "Dual-Channel Telephone Optical Terminal"
• "Dual Physically Isolated Ethernet Telephone Optical Terminal"
• "Dual-Channel Voice Optical Terminal"
• "Dual Physically Isolated Network Telephone Optical Terminal"
• "Dual Optical Port Telephone Optical Terminal"
• "Chain Network Telephone Optical Terminal"
• "Ring Network Telephone Optical Terminal"
  description: "The IDM NTD421 multi-service optical terminal provides a 250M optical interface, offering 2 telephone channels + 2 groups of physically isolated 100M Ethernet ports, where ports 1, 2, 3 and the fourth port are physically isolated, with 220V power supply. The IDM NTD421 multi-service optical terminal supports point-to-point applications with dual optical ports for mutual backup. It provides a standard SNMP network management interface."
  cover: "/images/imports/img-5885871b.webp"
  images:
• "/images/imports/img-5885871b.webp"
• "/images/imports/img-1925a4d4.webp"
• "/images/imports/img-72c01bc4.webp"
• "/images/imports/img-10fe9d23.webp"
• "/images/imports/img-9d062fe4.webp"
• "/images/imports/img-400c7e8e.webp"
• "/images/imports/img-5afacaf1.webp"
• "/images/imports/img-159af0db.webp"
• "/images/imports/img-feffe3d5.webp"
  specs:
  "Transmission Distance": "20Km, optional long-distance optical modules available for extended fiber transmission"
  keywords: "Multi-Service Optical Terminal,Telephone Media Converter,Dual-Channel Telephone Optical Terminal,Dual Physically Isolated Ethernet Telephone Optical Terminal,Dual-Channel Voice Optical Terminal,Dual Physically Isolated Network Telephone Optical Terminal,Dual Optical Port Telephone Optical Terminal,Chain Network Telephone Optical Terminal,Ring Network Telephone Optical Terminal"
  slug: "idm-ntd421"
  publishDate: "2026-05-12"

I. Overview

The IDM NTD421 dual-channel Telephone Optical Terminal is a new-generation optoelectronic integrated transmission device developed by our company, based on high-speed fiber optic transmission technology and PCM technology. It integrates Ethernet transmission and PCM multi-service access functions, meeting the demands of users for fiber optic transmission and access of both broadband and narrowband multi-services.

The IDM NTD421 is a fiber access device with multiple configurations. It provides fiber optic multiplexing of Ethernet, telephone, and serial ports, and can interoperate with IDM MP200 series optical interface devices.

The fiber optic interface rate of the IDM NTD421 is 150M, providing 1 wire-speed 100M Ethernet port.

The IDM NTD421-MP200S provides two physically isolated Ethernet channels, where interfaces 1, 2, and 3 share one wire-speed 100M Ethernet port, which can be isolated via VLAN partitioning. The 4th Ethernet group is physically isolated, providing a dedicated 100M bandwidth Ethernet port.

The fiber optic interface rate of the IDM NTD421-MP200 is 250M, providing 2 wire-speed 100M Ethernet channels, and can also provide transmission channels equivalent to 18 E1 bandwidths.

The IDM NTD421 provides up to two groups of fiber optic interfaces on the line transmission interface, forming mutual backup optical ports, or chain networks, ring networks, etc.

On the user interface, it provides 4 groups of Ethernet interfaces, 2 telephone channels (CO-side, RT-side, magneto, 2-wire audio), 2 RS485 channels or 1 RS422 channel. The Ethernet interfaces can be configured in physically isolated or VLAN isolated modes.

    II.  Device Operating Principle

III.  Product Features

Ø  Dual physically isolated wire-speed 100M Ethernet channels;

Ø  The 3 shared 100M Ethernet ports can also be isolated via VLAN partitioning;

Ø  Voice interfaces can be FXO CO-side automatic telephone, FXS RT-side automatic telephone, or MAG magneto telephone;

Ø  1 optional RS485 data channel;

Ø  Optical ports are SFP interfaces, allowing optical modules to be configured as required;

Ø  Can be customized with dual optical ports to form a chain network.

IV.  Single Optical Port Device Functions and Applications

Ø  Functions

u  Point-to-point general-purpose Telephone Optical Terminal diagram

u  Point-to-point magneto Telephone Optical Terminal

u  Point-to-point elevator five-party intercom Telephone Optical Terminal

u  Includes point-to-multipoint central office equipment

Ø  Applications:

u  Fiber to the office, physical isolation between internal and external networks;

u  Public security checkpoint information point construction

u  Shielded room communication

u  Armed police and public security guard booths

u  Community and factory information point construction

V.  Dual Optical Port Device Functions and Applications

Ø  Functions

u  Dual optical port chain network Telephone Optical Terminal interface annotation diagram

u  Chain network topology diagram with IDM MP200-30E

Ø  Applications

u  Tunnel construction applications

u  River monitoring and management

VI.  Technical Specifications

1)       Optical Interface

Interface Type

FC

Fiber Mode

Single-mode(Multi-mode optional)

Tx/Rx Rate	250M/250M	Tx/Rx Wavelength	1310nm/1550nm
Optical Output Power	-12~-6dBm	Receiver Sensitivity	Better than-18dBm

Transmission Distance

20Km, optional long-distance optical modules available for extended fiber transmission

2) Ethernet

Interface Type

RJ-45

Transmission Rate

10M/100M/1000Mauto-negotiation

Standard Protocol

SupportsIEEE802.3

Operating Mode

Full/Half Duplex/Auto-Negotiation

3) FXO, FXS Interfaces

Audio Range

300Hz~3400Hz

Compression Rate

A-law per ITU G.711

Impedance

Three-element compound impedance200Ω+560Ω//0.1μF

Loop Current

20mA/channel

4) Power Supply and Power Consumption

Power Supply

AC220V/DC-48V

Total Power Consumption

≤90W

5) Environmental Conditions

Operating Temperature

-10oC ~+50oC

Relative Humidity

0~95%(non-condensing)

6) Product Dimensions

Length×Depth×Height

××(mm)

VII. Application Examples