RAD ASMi-31 Sync/Async 2-Wire Manageable IDSL Modem

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ASMi-31 Async/Sync Short Range Modem with Management

RAD ASMi-31 Sync/Async 2-Wire Manageable IDSL Modem

  • The ASMi-31, Remote Control Sync/Async Short Range Modem, operates full duplex over twisted pair, 2-wire unconditioned lines. It has a transmission range of up to 8 km (5 miles) over 24 AWG wire (see Table 1) and operates at user selectable rates from 1.2 kbps to 128 kbps.
  • The modem uses 2B1Q line code and adaptive equalizers, which provide immunity to background noise, eliminate normal line distortion and enable efficient transmission over 2-wire twisted pair cables.
  • Transmit timing is either provided internally, or recovered from the received signal (user-selectable). Alternatively, the transmit timing can be detected automatically and derived externally from the digital interface, enabling tail-end applications. The carrier may be continuous or controlled by RTS, for passing control signals end-to-end (user-selectable).
  • ASMi-31 supports a wide range of digital interfaces: V.24/RS-232, V.35, X.21, RS-530, V.36/RS-449 and G.703 Codirectional (64 kbps). In addition, an Ethernet/802.3 bridging option enables direct connections of an Ethernet LAN to both sides of the ASMi-31 link.
  • The ASMi-31 system configuration is stored in non-volatile memory, minimizing system down-time when power is down or when a faulty remote unit is replaced.
  • Setup, status, alarms and diagnostics can be monitored and activated from the ASMi-31 front panel, or via a standalone portable control unit (PCU). Alternatively, the ASMi-31 can be managed from an ASCII terminal or an SNMP Unix/PC station connected to LRS-12/24.
  • Line interface circuitry protects against lightning and power surges.
  • ASMi-31 is available as a standalone unit in both ASMi-31/M "Master" and ASMi-31/S "Slave" versions. The master version has a front panel LCD and control switches. The slave unit has a blank panel, which prevents unauthorized changes to link parameters. ASMi-31 is also available as a card for central solutions.


  • 2-wire, full duplex, short range modem
  • Remote management using an in-band channel
  • 2B1Q line coding
  • Operating range up to 8 km (5 miles) over 24 AWG wire, independent of data rate
  • Real-time alarm indication for local and remote units
  • Selectable data rates from 1.2 kbps up to 128 kbps
  • Fully compatible with ASM-31 and SRM-31
  • Works opposite MP-2100/HS-U module and U-RPT (ASMi-31-2 only)
  • Card version for ASM-MN-214 19" rack and LRS-12 19" rack with central SNMP management
  • Configuration and monitoring of local and remote units from front panel
  • V.54 and built-in BER tester diagnostics
  • Supports various digital interfaces: V.24/RS-232, V.35, X.21, V.36/RS-449, RS-530, G.703 Codirectional, or built-in Ethernet bridge
  • Automatic rate detection in external clock mode




Figure 1. Central Site Application

Figure 2. ASMi-31 Working Opposite HS-U card in Megaplex-2100


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