RAD ASM-40 High Speed Short Range Modem

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ASM-40 High Speed Sync Shorthaul Modem

RAD ASM-40 High Speed Short Range Modem

  • The ASM-40, High Speed Synchronous Short Range Modem, operates full duplex over unconditioned lines at 13 selectable data rates up to 2048 kbps. The unit can also be used as a rate/interface converter. Transmission range is up to 1.75 km / 1.1 miles.
  • Transmission baud rate on the link is selectable:

      2048 for data rates of 32, 64, 128, 256, 512, 1024 and 2048 kbps

      1536 for data rates of 92 (special order instead of the 1544), 384, 768 and 1536 kbps

      1544 for data rates of 1544 kbps

      1920 - special ordering option for 1920 kbps, instead of 1544 kbps.

    The digital port data rate can differ from the line baud rate, enabling ASM-40 to be used as a rate converter.

  • Zero suppression on the link is strap-selectable for either AMI, HDB3, or B8ZS coding, according to ITU G.703 standard.
  • The digital port has modular, field changeable interfaces: V.35, X.21, V.36/RS-449, RS-530, IR-ETH or G.703/HDB3 (see Ordering). The G.703/HDB3 interface supports (strap-selectable) data rates of 128, 256, 512, 1024, or 2048 kbps.
  • Transmit and receive timing can be provided internally, or derived externally from the data terminal or receive signal. Internal FIFOs provide jitter attenuation or phase difference correction either from the incoming analog signal (line side) or from the external clock on the DTE side.
  • Selectable forward error correction detects either random or burst errors for rates up to 1024 kbps. Encoding/decoding of data is by Golay (23, 12) error correction mode, which allows random error correction of up to 3 bit errors in a 23-bit frame, or single burst correction of up to 9 bits in a 72-bit frame.
  • ASM-40 has a special ordering option for remote power feeding of repeaters ( ASM-40/P. This option works together with the external power supply PS-RPT-2 or PS-RPT-8, and provides power for up to 6 repeaters on each side of the link. When power feeding is used in conjunction with PS-RPT power supply, no special ordering option is required. (PS-RPT should be ordered separately).
  • ASM-40 meets special standards. It is approved for AUSTEL (A95/76A/0020), TUV (E9471050.01), BABT and NET-1.
  • Diagnostic capabilities comply with ITU V.54, and feature local analog loopback, and local and remote digital loopback. Loopbacks can be activated by front panel switches or by toggling the assigned pins on the digital port (V.35, V.36/RS-449 or RS-530 only). The product includes an internal 511-bit pseudo random pattern generator and BER tester for complete end-to-end integrity testing. The BER tester results are displayed on an error LED, which indicates each bit detected.
  • Line protection is available using isolation transformers and a protection circuitry. This protects ASM-40 and the attached DTE from line hazards such as AC or DC overvoltages.
  • ASM-40 is available as a standalone unit or as a card version for the ASM-MN-214 19" modem rack. The rack can support up to 14 cards and is supplied with 25-pin D-type digital port connectors. Modems with X.21 or V.35 interface require an external mechanical adapter. CIA/X.21 can be ordered for converting two adjacent DB-25 connectors to two X.21 15-pin connectors, CIA/V.35 for converting one DB-25 connector to a V.35 34-pin connector.
  • Optional hardware is available for mounting one or two standalone units in a 19" rack.


  • Extended range, baseband modem - up to 2048 kbps
  • Can be used as a modem or as a rate/interface converter
  • Transmission range of up to 1.75 km (1.1 miles)
  • Full duplex transmission over 4 wires
  • Modular digital interfaces include: V.35, X.21, IR-ETH, RS-530, V.36/RS-449 or G.703/HDB3
  • Jitter attenuation complies with G.823 (for CEPT) and AT&T 62411-1985 (for T1)
  • Remote power feeding option for repeaters
  • Meets special Telecom standards (Austel, BABT)
  • Selectable Forward Error correction for rates up to 1024 kbps

Short Range Modem, standalone unit with internal power supply,
with special Telecom approvals

Short Range Modem card for
ASM-MN-214 19" rack
Note: When using V.35 or X.21 interfaces, the CIA adapter is required.

Short Range Modem, standalone unit with special telecom approvals

Short Range Modem, standalone unit with remote power feed

* Specify standalone and rack
main power supply:
115 for 115 VAC
230 for 230 VAC
48 for -48 VDC
24 for 24 VDC
# Specify digital interface:
V35 for V.35
X21 for X.21
530 for RS-530
36 for V.36/RS-449
703 for G.703/HDB3 with DB-15 connector
703UB for unbalanced
G.703/HDB3 with BNC connector
UTP for built-in Ethernet/802.3 bridge
with RJ-45 connector
(available in standalone and card versions CF and CB)
BNC for built-in Ethernet/802.3 bridge
with BNC connector
(available in standalone only)
Specify standalone line interface:
(default is balanced, terminal block)
B for balanced, 120 with DB-15 connector
UB for unbalanced 75 with BNC connection
& Specify 1920 kbps option:
1920 for 1920 kbps
$ Specify modem card line impedance:
(default is 120)
UB for unbalanced 75
+ Specify line interface:
TB for balanced, 120 with terminal block connector
UB for unbalanced, 75 with BNC connector
B for balanced, 120 with DB-15 connector

Connector Interface Adapter for the
ASM-MN-214 19" rack

~ Specify CIA connector option:
V35 for adapting one modem card's
25-pin connector into one V.35, 34-pin connector
X21 for adapting two adjacent modem cards' 25-pin
connectors to two X.21, 15-pin connectors

Hardware for mounting one or two standalone ASM-40 units in a 19" rack.
For power feeding, order the
PS-RPT2 or the PS-RPT8, and the CBL-ASM-40 cable




Figure 1 -
Short Range Modem for Point-to-Point Link

Figure 2 -
Rate and Interface Converter for Accessing Long Range Digital Networks

Figure 3 -
Extended Digital Network Access using Repeaters

Figure 4 -
Interface Conversion



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