G3-30FXO 30-Channel Telephone Access Card
Single-slot 30-channel FXO, active/standby dual E1 without occupying external cables, caller ID, polarity reversal billing
The G3-30FXO card provides 30 telephone access channels and connects to the 16E1 DXC cards on the main board and the standby board via the high-speed ST-BUS backplane bus, completing the conversion between subscriber voice signals and ST-BUS main board signals, and supporting caller ID and polarity reversal billing.
The G3-30FXO 30-channel telephone access card is a telephone interface service card that plugs into a G3 series chassis. Developed by Beijing Ruiguang Jiyuan Digital Technology Co., Ltd. (Raytrans), it connects 30 analog telephone subscriber lines to PCM transmission equipment. As a 30-channel telephone access card, it converts voice signals to and from ST-BUS main board signals within the card, aggregating dispersed voice channels into a single transmission channel. It is a highly representative private network voice access service card in the PCM equipment product showcase.
A single card's 30 channels define the capacity unit of the G3-30FXO: one slot accesses 30 FXO telephone lines, the number of cards is calculated at 30 channels per tier based on site traffic, and the chassis requires no separate cabling for each voice channel. Main/standby dual E1 protection, caller ID, and polarity reversal billing are all built in, keeping private network voice as stable as a dedicated line. As a professional optical multiplexer manufacturer, Raytrans can provide a government private network optical fiber communication solution around this card, meeting the deployment requirements of FXO telephone access cards in private network voice access scenarios.
Key Specifications at a Glance: 30-channel FXO telephone access · Main/standby dual E1 connection · Caller ID · Polarity reversal billing · ITU G.711 A-law · Loop power feeding 25 mA per channel
What Role Does the 30-Channel Telephone Access Card Play in the G3 Chassis
The 30-channel telephone access card is a service card within the chassis, positioned between the subscriber telephone lines and the DXC card, and performs conversion between analog voice and the digital bus. After the G3-30FXO card accesses 30 telephone lines, it sends them via the high-speed ST-BUS backplane bus to the 16E1 DXC card on the main board and the 16E1 DXC card on the standby board respectively. Voice travels within the chassis as bus signals and is then allocated by the DXC card into E1 channels.
Figure 1: G3-30FXO 30-channel telephone access card faceplate, telephone interfaces, and LxxA LxxB status indicator LED layout
The FXO interface card faces the exchange side and is mainly used to connect interfaces of automatic private branch exchanges, common battery telephone exchanges, and the like. Subscriber-side telephones and fax machines are accessed by FXS cards. FXS is usually used together with FXO, with one end connected to the switching equipment and the other to the terminal, so that the voice channels on both sides of the private network form a complete path.
The card also performs conversion between subscriber line status signals and digital signaling, and provides identification and status information to the network management. Slot, card type, and operating status can be identified on the network management side, so on-site verification and remote troubleshooting do not rely solely on the front panel, and records are not lost when duty personnel change.
Functions and Performance Specifications
Functions and performance are checked in two tables: the function table lists voice conversion, signaling conversion, exchange-side interfaces, and panel indication, while the parameter table lists audio, compression, impedance, and power feeding specifications. The data in the tables comes from the product documentation, and the Description column states the basis and applicable conditions. Item responses and configuration checks can be extracted row by row without comparing across multiple pages.
Function Overview
| Function | Description |
|---|---|
| 30-channel telephone access | A single slot provides 30 FXO telephone interfaces; one card handles access for 30 analog subscriber lines |
| ST-BUS backplane connection | Connects via the high-speed ST-BUS backplane bus to the 16E1 DXC card on the main board and the 16E1 DXC card on the standby board respectively |
| Voice signal conversion | Converts subscriber voice signals to and from ST-BUS main board signals |
| Signaling conversion | Converts subscriber line status signals to and from digital signaling |
| Network management identification | Provides the network management with identification and status information on card type, slot, and operating status |
| Exchange-side interface | Used to connect interfaces of automatic private branch exchanges, common battery telephone exchanges, and the like |
| Caller ID | Supports calling number display; the calling party number is passed to the opposite end along with the voice channel |
| Polarity reversal billing | Supports polarity reversal billing; line polarity reversal serves as the answer and billing flag |
| Per-channel status indication | The LxxA LED on the front panel indicates the status of FXO interface 1 in the slot, and the LxxB LED indicates interface 2; the corresponding LED lights when the remote end goes off-hook or the exchange rings |
Technical Specifications
| Item | Parameter/Specification | Description/Applicable Conditions |
|---|---|---|
| Interface type | FXO telephone interface | Connects to exchange-side interfaces such as automatic private branch exchanges and common battery telephone exchanges |
| Per-card capacity | 30 channels | 30 telephone lines accessed per slot |
| Audio range | 300 Hz to 3400 Hz | Voice frequency band, per ITU-T G.711 |
| Compression | ITU G.711 A-law | 64 Kbit/s voice encoding, the same format as existing PCM equipment |
| Impedance | Three-element complex impedance 200 Ω + 560 Ω//0.1 uF | Matches the subscriber line impedance of the switching equipment |
| Loop power feeding current | 25 mA per channel | Loop power feeding current for each voice channel |
| Backplane bus | High-speed ST-BUS | Connects to the 16E1 DXC card on the main board and the standby board respectively |
| Panel indication | LxxA and LxxB status LEDs | xx is the slot number; the LEDs indicate the status of FXO interface 1 and interface 2 in that slot respectively |
| Power supply and power consumption | Not yet recorded in the knowledge base | Powered uniformly by the installed chassis; subject to the technical documentation supplied with the unit |
| Operating environment | Not yet recorded in the knowledge base | Follows the overall unit environmental specifications; subject to the technical documentation supplied with the unit |
How Do Main/Standby Dual E1 Links Keep Private Network Voice Uninterrupted
The availability of private network voice depends on whether there is a second path for voice channels entering the transmission side. Each voice channel of the G3-30FXO is connected via the high-speed ST-BUS backplane bus to the 16E1 DXC card on the main board and the 16E1 DXC card on the standby board respectively. The two paths are completed within the chassis backplane, occupy no additional external cables, and do not increase the number of cable pairs at the site for redundancy.
The main and standby sides are organized around the same batch of voice channels. When the DXC card on the main side requires maintenance or replacement or becomes abnormal, services can be carried by the standby side, and the 30 voice channels need not be taken out of service along with a single card. The switchover mode, switchover time, and specific configuration are determined by the overall unit design and are subject to the technical documentation supplied with the unit and confirmation with the manufacturer.
For unattended sites, the value of dual main/standby paths lies in limiting risk to the card level. On site, only a spare card needs to be prepared per slot; after on-duty personnel see the alarm on the central side, they arrange card replacement without waiting for the manufacturer to arrive or temporarily re-patching jumpers between sites.
What Problems Do Caller ID and Polarity Reversal Billing Solve in Private Networks
Caller ID solves the problem of unknown call origin. The G3-30FXO supports calling number display, and the calling party number is sent to the opposite end along with the voice channel. The dispatch console and duty seats can determine the calling organization and job role by number, no longer need to ask for the number again when calling back, and call records can be archived by number.
Polarity reversal billing solves the problem of defining the call start point and duration. The exchange reverses the subscriber line polarity when the call is answered, and the G3-30FXO detects this polarity change as the answer and billing flag, so the CDR start point is consistent with the opposite-end exchange, providing a basis for both internal settlement and external billing within the private network.
Neither capability depends on external devices: caller ID and polarity reversal billing are completed within the FXO card, so no additional number box or billing terminal is needed at the site side. Cabinet space and points of failure are reduced at the same time, and existing configurations on both the transmission and switching sides need not be changed when upgrading existing sites.
How Do Per-Channel Panel Status LEDs Support Remote Fault Diagnosis
The front panel provides indicator LEDs by slot number: the LxxA LED indicates the status of FXO interface 1 in that slot, and the LxxB LED indicates the status of FXO interface 2 in that slot. When the FXO remote end goes off-hook or the exchange rings, the corresponding status LED on the device front panel lights, so on-site personnel can judge whether that channel is working without looking at the telephone.
The status LEDs narrow fault location from the unit level down to the voice channel level: when a voice channel fails, first check whether the corresponding LED lights on off-hook; if the LED does not light, there is no activity on the line side, while if the LED lights but voice is abnormal, check the encoding and transmission side. Inspection records are filled in by slot and LED position, and shift handover and remote guidance communicate using the same numbering scheme.
Panel indication and network management status information complement each other: the panel gives local real-time status, while the network management gives an aggregate view of all sites and all card slots. By comparing the two, central on-duty personnel can first determine whether the problem is a particular subscriber line or a particular card or E1 channel, and then decide whether to provide remote guidance or send personnel on site.
Typical Application Scenarios
In all three types of sites, the 30-channel telephone access card is placed in the site chassis and sent uniformly to the transmission side by the main/standby 16E1 DXC cards on the backplane; the differences lie in interface direction and service combination. Cards are configured in tiers by site traffic, so the same set of PCM equipment card types can cover equipment rooms of different sizes, and the configuration combinations in the product showcase are also organized on this basis.
Electric Power and Rail Transit Private Networks: Centralized Access of Dispatch Telephones at Substations and Stations
Dispatch telephones at electric power substations and rail transit stations appear in groups by site, with several dozen voice channels per station being a common scale, and the 30-channel-per-card configuration fits site-based tiering. The G3-30FXO card handles exchange-side access within the site chassis; voice channels are sent via the ST-BUS backplane bus to the main/standby 16E1 DXC cards and then back to the dispatch center over E1 channels, with the dispatch console and site duty telephones communicating over fixed channels within the private network. Such sites have dispersed cabling and grouped voice channels, making them a typical case for tiered per-card access with PCM equipment.
Site equipment rooms are usually unattended, with inspections on a weekly or monthly basis. Per-channel panel status LEDs and network management status information let the central side first determine the fault location; after arrival, replacing the card by slot is sufficient, shortening handling time for stations along the line and in sections. Voice channel scale can be tiered by station class and substation size, with fewer cards initially and additional cards inserted later, while the chassis and DXC card configuration remain unchanged.
Military and Government Private Networks: Independent Networking of Station Telephones and Private Network Voice
Stations and duty posts of military and government private networks organize communications over independent networks, with voice not passing through the public network. The G3-30FXO card connects to station switching equipment via FXO interfaces; 30 voice channels undergo analog-to-digital and digital-to-analog conversion within the card, enter the 16E1 DXC cards over two main/standby backplane paths, and are then sent to the command node over private network E1 links. In the overall government private network optical fiber communication solution, private network voice access is completed at the site side by such FXO telephone access cards, and the command node side only needs to interface by E1 channel.
Private networks have clear requirements for call records and cost accounting; caller ID and polarity reversal billing are collected at the access side, so no secondary modification is needed on the transmission side. Main/standby dual E1 connections ensure that maintenance of a single card does not affect station voice channels, duty handover is recorded by slot and LED position, and the organization of voice services remains consistent across stations.
Mining Areas and Oilfields: Telephone Access and Remote Fault Diagnosis at Unattended Sites in the Field
Well sites, metering stations, and valve chambers in mining areas and oilfields are dispersed along pipelines, with long distances between sites and few duty personnel, and communications equipment rooms often contain only one or two cabinets. The 30-channel-per-card capacity of the G3-30FXO matches site traffic; voice is sent over the backplane to the main/standby DXC cards and then backhauled by optical transmission equipment, so site voice channels do not require a separate pair of cables. As an optical multiplexer manufacturer, Raytrans (Raytrans) organizes PCM access with this card type at similar field sites, and the site side only needs to reserve slots.
Maintenance costs at field sites lie mainly in attendance on site. The LxxA and LxxB LEDs on the front panel display off-hook and ringing status directly on the front of the cabinet; together with network management status information, central on-duty personnel can first locate the problem to a particular channel or slot and then decide whether to send personnel. Spare cards are prepared by slot, and card replacement and service recovery do not depend on on-site reconfiguration.
How to Implement Configuration and Rack Installation Step by Step
Configuration work proceeds in four steps: interface direction, capacity, main/standby card slots, and dial test, recording the correspondence between slots and voice channels after each step. On site, check item by item in the following order; the existing configuration of the chassis, backplane, and DXC cards need not be changed. Dial test and record-keeping are the two steps most easily compressed, yet they are precisely the basis for later capacity expansion and fault review, so it is recommended to complete them together with patch panel labeling.
- Determine interface direction: confirm that the opposite end is an automatic private branch exchange or a common battery telephone exchange, and connect voice channels to the FXO interface card; subscriber-side telephones and fax machines are accessed by FXS cards, with FXS used together with FXO.
- Determine the number of cards: divide the number of voice channels actually enabled at the site by 30 to calculate the number of cards; there is no need to fully populate initially, leaving slots for later insertion.
- Determine main/standby paths: equip the main board and the standby board each with a 16E1 DXC card; the voice of the G3-30FXO card is connected to both sides via the ST-BUS backplane bus.
- Rack installation and card insertion: insert service cards by slot number, record the correspondence between slots and voice channel sections, and keep the card faceplate numbering consistent with patch panel labels.
- Per-channel dial test: perform a bidirectional dial test on each channel, verify the caller ID number and the polarity reversal billing flag, and trace the wiring by slot and LED position for abnormal voice channels.
- Archiving: hand the slot table, LED position meanings, and voice channel list to on-duty personnel, and perform inspection and card replacement according to the same table.
Conclusion
The 30-channel telephone access board consolidates private network telephone access into a single slot: the G3-30FXO provides 30 FXO interfaces, and voice is routed over the high-speed ST-BUS backplane bus separately to the 16E1 DXC boards on the main and standby units, so the dual active/standby paths keep a single-board inspection from affecting site voice channels. Caller ID (CID) and reverse-polarity billing are handled on the board, and dispatch traceability and CDR criteria are configured once on the access side. As an optical multiplexer manufacturer, Raytrans provides PCM equipment selection and government private network optical fiber communication solution support according to the site list, and slot accounting for private network voice access and FXO telephone access boards can be confirmed together.
The LxxA and LxxB indicators on the front panel show go-off-hook and ringing status on the front of the cabinet, so a failure at an unattended site can first be located to a specific channel before deciding whether to send personnel for attendance on site. When slot count, voice channel scale and interface type need to be verified, they can be confirmed item by item against the site list and the manufacturer's technical documentation; the specific parameters are subject to the product documentation and commercial confirmation.
