IDM-120N 60-Channel Telephone Optical Multiplexer
120-channel telephone
The IDM-120N 60-channel telephone optical multiplexer is a PCM integrated service optical fiber transmission equipment designed with dedicated large-scale integrated circuits. It has a total optical fiber bandwidth of 155M and provides 2 channels of shared 100M Ethernet, 4 groups of E1 transparent transmission interfaces, and 120 telephone subscriber channels. It supports dual backup and hot-swappable power cards and ringing current cards.
What is a 120-channel telephone 4-channel E1 optical multiplexer?
The IDM-120N 60-channel telephone optical multiplexer is a 120-channel telephone 4-channel E1 optical multiplexer developed by Beijing Ruiguang Jiyuan Digital Technology Co., Ltd. It adopts dedicated large-scale integrated circuit design and is used to simultaneously carry 120 telephone subscriber channels, 4 groups of E1 transparent transmission interfaces, and 2 channels of shared line-rate Fast Ethernet service over a single 155M optical fiber link. As a representative product of Raytrans, a professional optical multiplexer manufacturer, this device has typical product showcase value in the fields of telephone optical multiplexers and multi-service optical multiplexers.
The IDM-120N 60-channel telephone optical multiplexer organizes narrowband voice channels and E1 channels according to the PCM30/31 format. The E1 transmission channels comply with the ITU-T G.703 standard, and the FXO and FXS interfaces support polarity reversal and caller ID. The power card and power and ringing current card are configured in 1+1 mode and support hot-swappable replacement. The unit is a 19-inch 3U chassis with 19 card slots. The device can be widely used in public telephone network services of telecommunications and Netcom, as well as leased-line information and data services in sectors such as electric power, banking, public security, and military. It is also a commonly used optical multiplexer in government private network optical fiber communication solutions and military emergency communications vehicle solutions.
Key specifications at a glance: 120 telephone channels · 4 groups of E1 · 2 channels of shared line-rate Fast Ethernet · 155M optical fiber transmission bandwidth · 1+1 hot-swappable dual backup of power card and ringing current card · 19-inch 3U chassis with 19 card slots
Figure 1: IDM-120N 60-channel telephone optical multiplexer 19-inch 3U chassis front view with card slots and alarm indicator LED close-up
The IDM-120N 60-channel telephone optical multiplexer adopts a card-based structure. The 120 telephone voice channels are inserted as service cards, and the chassis reserves multi-function card slots for flexible expansion as services grow, supporting chain, star, and other arbitrary network topologies. The front panel provides function control switches and alarm indication, and together with online network management, enables online real-time configuration, query, and fault statistics management of the device.
How does the PCM30/31 format fit 120 telephone channels into 4 groups of E1
The PCM30/31 format is the organization method for E1 primary group voice channels. The IDM-120N 60-channel telephone optical multiplexer encodes analog telephones into 64Kbps digital voice according to this format and places them into E1 channels for transmission. A single voice channel uses ITU-T G.711 A-law compression, with an audio range of 300Hz to 3400Hz and a loop current of 25mA per channel, meeting PSTN telephone quality requirements. The E1 channels have a bit rate of 2048Kbps, HDB3 line coding, and channel-associated signaling, and the 4 groups of E1 together provide 120 telephone subscriber channels. The three types of services—telephone, E1, and Ethernet—are transmitted independently over the same optical fiber link without occupying each other's bandwidth.
What functions and interfaces does the IDM-120N 60-channel telephone optical multiplexer have?
The IDM-120N 60-channel telephone optical multiplexer provides the following functions centered on high-capacity voice channel aggregation and multi-service optical fiber transmission.
| Function | Description |
|---|---|
| 120-channel telephone voice channel aggregation | A single device provides 120 telephone subscriber channels. Both FXO and FXS interfaces support polarity reversal and caller ID, and are wired according to the exchange side or telephone side |
| 4 groups of E1 transparent transmission interfaces | Provides 4 groups of E1 channels with a bit rate of 2048Kbps and HDB3 line coding, compliant with ITU-T G.703, with selectable 75Ω/120Ω impedance, using channel-associated signaling for transparent transmission |
| 2 channels of shared line-rate Fast Ethernet | Provides 2 RJ-45 Ethernet interfaces, 10/100Base-T, 10M/100M rate, compliant with IEEE802.3, Adaptive half-duplex/full-duplex, sharing 100M line-rate bandwidth |
| 16 subscriber interface slots | The 19-inch 3U chassis provides 16 subscriber interface slots. 8-channel FXO/FXS service cards are inserted according to voice channel direction, and voice channel capacity is configured by combining service cards |
| 1+1 dual backup of power card and ringing current card | The power card PRU-120 and the power and ringing current card RPRU-120 are each configured in 1+1 mode, supporting hot-swappable replacement during operation, so that services are uninterrupted in the power supply and ringing stages |
| Multi-function card slot expansion | Reserves multi-function card slots for flexible expansion as services grow, supporting chain, star, and other arbitrary network topologies |
| Function control switches and alarm indication | The front panel provides function control switches and alarm indication for on-site commissioning and fault location |
| Online network management functions | Supports online real-time configuration, query, and fault statistics management via network management, and together with alarm indication enables centralized maintenance |
How many telephone and network channels can one optical fiber carry: how does single-fiber three-service save private network optical fibers
The IDM-120N 60-channel telephone optical multiplexer aggregates three types of services that previously required multiple stacked devices into a single 3U device. Traditional private network sites typically use one telephone optical multiplexer for subscriber line provisioning, one PDH optical multiplexer for E1 transmission, and one more Ethernet optical multiplexer for data backhaul, occupying multiple rack positions and multiple pairs of optical fibers. The IDM-120N 60-channel telephone optical multiplexer uses a total optical fiber bandwidth of 155M to uniformly carry 120 telephone channels, 4 groups of E1, and 2 channels of shared line-rate Fast Ethernet. The site side requires only one device and a pair of optical fibers, reducing the occupation of rack positions and optical fiber resources accordingly. For government private network optical fiber communication solutions and military emergency communications vehicle solutions, the high integration of this multi-service optical multiplexer is especially suitable for scenarios with tight rack positions and limited optical fiber resources.
At the service level, the three types of services—telephone, E1, and Ethernet—do not interfere with one another: E1 channels are transparently transmitted according to ITU-T G.703 and can interface with existing PCM and SDH equipment; Ethernet interfaces comply with IEEE802.3 and can be directly connected to IP devices such as switches and routers; and the 120 voice channels are configured in 8 channels per card according to FXO/FXS direction, so service cards can be added or removed according to the actual number of voice channels in a project.
| Differentiation Point | Value to users |
|---|---|
| Single-fiber three-service aggregation | A single fiber carries 120 telephone channels + 4 E1 + 2 100M Ethernet, saving private network optical fiber resources |
| 1+1 hot-swappable power and ringing current | 1+1 dual backup hot-swappable power card and ringing current card, ensuring uninterrupted telephone service at unattended sites |
| 19 card slots mixed insertion | 19-inch 3U chassis with 19 card slots, service cards can be mixed and inserted for smooth capacity expansion to 120 channels |
Unit card composition and how a 60-channel telephone optical multiplexer expands to 120 channels
A single IDM-120N 60-channel telephone optical multiplexer consists of an equipment chassis backplane, main control cards, power cards (power and ringing current cards), and FXO/FXS service cards. The models and functions of each card are as follows.
| No. | Name | Model | Description | Quantity |
|---|---|---|---|---|
| 1 | Equipment chassis backplane | IDM-120 | 19-inch 3U chassis, providing 19 card slots | 1 |
| 2 | E1 interface main control card | CMU-E1-120 | Provides E1 interface access | 1 |
| 3 | Optical interface main control card | CMU-120 | Provides 1 group of optical interface access, 2 groups of line-rate 100M Ethernet interfaces, and 4 groups of E1 interfaces | 1 |
| 4 | Power card | PRU-120 | Provides 1+1 power supply and power supply for the unit, used on the FXO side, -48V input | 2 |
| 5 | Power and ringing current card | RPRU-120 | Provides 1+1 power supply, power supply for the unit, and ringing voltage, used on the FXS side, -48V input | 2 |
| 6 | FXO service card | 8FXO-120 | 8 FXO interfaces, exchange side | As required |
| 7 | FXS service card | 8FXS-120 | 8 FXS interfaces, user side | As required |
Figure 2: IDM-120N 60-channel telephone optical multiplexer main control card, power card, and 8-channel FXO/FXS service card slot structure
In a single device configuration, only one of the E1 interface main control card and the optical interface main control card is selected. FXO/FXS service cards are configured in 8 channels per card within the 16 subscriber interface slots, and the specific number and direction of voice channels are subject to the project configuration.
The answer to how a 60-channel telephone optical multiplexer expands to 120 channels lies in this card-based structure: the 19-inch 3U chassis provides 19 card slots and 16 subscriber interface slots, and voice channel capacity grows with the number of FXO/FXS service cards, with a single device providing 120 telephone subscriber channels according to product documentation. When services grow, corresponding service cards are added according to voice channel direction, and the reserved multi-function card slots in the chassis can also carry subsequent expansion without replacing the entire unit.
IDM-120N 60-channel telephone optical multiplexer parameters and interface specifications
The following parameters cover optical interfaces, E1, Ethernet, telephone interfaces, and power supply and environment. They are based on IDM-120N product documentation and serve as a reference for networking design and equipment selection.
Optical Interface Parameters
| Item | Parameter/Specification | Description |
|---|---|---|
| Interface type | FC (SC and other interfaces can be customized) | Selected according to on-site optical fiber connectors |
| Fiber mode | Single-mode (multi-mode optional) | Single-mode is used for longer-distance transmission |
| Optical fiber rate | 155bps±50ppm | Corresponds to the 155M optical fiber transmission bandwidth of the unit |
| Wavelength | 1310nm | Single-mode fiber transmission window |
| Transmit optical power | -2～-11dBm | Transmit optical power range |
| Receiver sensitivity | Better than -36dBm | Optical reception performance specification; actual transmission distance is calculated according to the optical power budget |
E1 Interface Parameters
| Item | Parameter/Specification | Description |
|---|---|---|
| Bit rate | 2048Kbps | Standard E1 bit rate |
| Line coding | HDB3 | Complies with ITU-T G.703 line coding requirements |
| Standard protocol | ITU-T G.703 | E1 electrical interface standard |
| Impedance | 75Ω/120Ω | Coaxial or balanced interface optional |
| Frame structure | PCM30/31 | Voice channels are organized according to the PCM30/31 format |
| Signaling | Channel-associated signaling | A commonly used signaling method for interfacing with SPC switching offices |
Ethernet Interface Parameters
| Item | Parameter/Specification | Description |
|---|---|---|
| Interface type | RJ-45 | Ethernet electrical interface |
| Transmission rate | 10/100Base-T, 10M/100M | Rate adaptive |
| Standard protocol | IEEE802.3 | Ethernet standard protocol |
| Operating mode | Full/half duplex/adaptive | Can be directly connected to Ethernet devices such as switches |
FXO/FXS Telephone Interface Parameters
| Item | Parameter/Specification | Description |
|---|---|---|
| Audio range | 300Hz～3400Hz | Telephone voice band |
| Impedance | Three-element complex impedance 200Ω+560Ω//0.1μF | Return loss characteristics of the telephone interface |
| Compression | ITU-T G.711 A-law | Voice codec |
| Loop current | 25mA per channel | Feeding capability for the telephone set |
| Additional functions | Polarity reversal, caller ID | Supported by both FXO and FXS interfaces |
Power Supply, Environment and Chassis
| Item | Parameter/Specification | Description |
|---|---|---|
| Power supply mode | DC-48V or AC 220V | Selected according to equipment room or on-site power supply conditions |
| Overall power consumption | ≤250W | Upper limit of overall power consumption |
| Operating temperature | 0℃～+40℃ | Suitable for indoor equipment room environment |
| Humidity | 95% non-condensing | Relative humidity requirement |
| Product dimensions | Length×Depth×Height 480×200×132mm | 19-inch 3U chassis installation dimensions |
Typical application scenarios: electric power private network, rail transit, and military and government private networks
Figure 3: IDM-120N 60-channel telephone optical multiplexer application diagram of telephone, E1 and Fast Ethernet networking over a single fiber
Electric Power Private Network: Telephone and Data Services over the Same Fiber at Substations
Sites of an electric power private network usually need to enable dispatching and office telephone services at the same time, and to interconnect with E1 leased line channels carrying automation data. After deploying the IDM-120N 60-channel telephone optical multiplexer at substations, power supply stations and other sites, telephone services are provisioned through FXO/FXS interfaces, E1 channels carry leased-line data through transparent transmission in accordance with ITU-T G.703, and 2 Fast Ethernet interfaces backhaul IP services. A pair of optical fibers completes all access, with no need to configure a separate transmission device for telephone and data. The power card and the power and ringing current card support 1+1 dual backup and hot-swappable operation, so they can be replaced online during maintenance of the power supply or ringing unit at the site, and voice channel services do not have to be interrupted for a long time.
Rail Transit Communication: Centralized Backhaul of Telephone and Network Services at Stations along the Line
Metro and conventional railway lines have a large number of equipment rooms at stations along the line and in tunnel sections, which are widely distributed, and telephone, E1 trunk and network data services need to be aggregated back to the center. The IDM-120N 60-channel telephone optical multiplexer at equipment rooms along the line accesses telephone voice channels, 4 groups of E1 and 2 Fast Ethernet interfaces on one device at the same time, and transmits them to the central node over a pair of optical fibers. The 19-inch 3U chassis is suitable for installation in a standard cabinet, and DC-48V or AC 220V power supply can be selected according to the power supply conditions of the equipment room along the line. The front panel provides alarm indication, and together with the network management system, the operating status of each station can be monitored remotely, reducing the inspection frequency along the line.
Military and Government Private Network: Voice and Leased-Line Assurance for Unattended Sites
Sites of military and government private networks are often unattended and have high requirements for voice quality and link availability. The IDM-120N 60-channel telephone optical multiplexer carries 120 voice channels plus E1 and Ethernet services over 155M optical fiber bandwidth. Voice adopts A-law encoding in ITU-T G.711, and E1 complies with ITU-T G.703 and the PCM30/31 format, so it can intercommunicate with existing transmission equipment of the private network. The power card and the power and ringing current card support 1+1 dual backup and hot-swappable operation, so a single board failure can be replaced during operation, and services are uninterrupted in the power supply and ringing links. The network management system can perform online real-time configuration, query and fault statistics on the on-site equipment, facilitating centralized maintenance.
Conclusion: How to Select a 120-Channel Telephone 4-E1 Optical Multiplexer
The 120-channel telephone 4-E1 optical multiplexer is suitable for private network nodes that need high-capacity telephone subscriber line provisioning while also supporting E1 and Ethernet services. The IDM-120N 60-channel telephone optical multiplexer packs 120 voice channels, 4 groups of E1 and 2 shared line-rate Fast Ethernet interfaces into one 19-inch 3U device over 155M optical fiber bandwidth. During selection, determine the number of FXO/FXS service cards according to the voice channel direction, select FC (SC and other interfaces can be customized) optical interfaces and single-mode (multi-mode optional) optical fibers according to optical fiber resources, and select DC-48V or AC 220V according to the on-site power supply conditions. For unattended sites with high reliability requirements, the 1+1 hot-swappable dual backup design of the power card and the power and ringing current card can be used, together with online network management, to achieve centralized maintenance of configuration, query and fault statistics. The device has an operating temperature of 0℃～+40℃ and a humidity of 95% non-condensing, and is recommended for deployment in an indoor equipment room environment. For the specific configuration, it is recommended to confirm with the optical multiplexer manufacturer based on project requirements.
