RAD ASM-45 High Speed Short Range Modem

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ASM-40 High Speed Sync Shorthaul Modem

RAD ASM-45 High Speed Short Range Modem

  • The ASM-45, Short Range Modem, operates synchronously, full duplex over unconditioned lines, at a range of up to 5.5 km (3.5 miles). ASM-45 operates at seven selectable data rates up to 768 kbps.
  • The digital interfaces available are:
    • RS-530
    • V.35
    • X.21
    • V.24/RS-232 (up to 64 kbps only)
    • G.703 Codirectional (64 kbps).
  • Conditioned diphase modulation (EUROCOM Std. D1) provides immunity to background noise, eliminates normal line distortion and enables efficient transmission and reception of serial data over twisted pair cable.
  • Transmit timing is provided either internally, or is derived externally from the data terminal or from the receive signal. Receive timing is regenerated from the received signal.
  • ASM-45 features V.54 diagnostic capability to perform local analog loopback, and local and remote digital loopback tests. Loopback is controlled by either a manual switch or via the digital interface signals (excluding X.21 and G.703 interfaces). The front panel switch generates a pseudo-random test pattern (511 bits) according to ITU, for testing end-to-end connectivity. An ERROR LED flashes for each bit error.
  • ASM-45 incorporates interface circuits for the terminal/computer, an automatic equalizer, and a modulator/demodulator. Line coupling is through isolation transformers which, in conjunction with other circuitry, protect against AC or DC overvoltages.
  • ASM-45 is available as a standalone (desk-top) unit or as a card for the ASM-MN-214 19" modem rack. DTE connectors on the rack are 25-pin D-type, female. 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, or CIA/V.35/1 for converting one DB-25 connector to a V.35 34-pin connector.


  • Synchronous transmission over 4-wire
  • Selectable data rates: 64, 128, 192, 256, 384, 512 or 768 kbps
  • Range up to 5.5 km / 3.5 miles at 64 kbps over 24 AWG cable
  • Carrier control
  • V.54 diagnostics
  • Internal test pattern generator (V.52) and special error LED
  • Variety of digital interfaces: RS-530, V.35, X.21, V.24 (64 kbps only) or G.703 Codirectional (64 kbps)

Short Range Modem, standalone unit

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

19" modem rack for 14 modem cards

* Specify supply voltage for the standalone and the rack's main power supply:
115 for 115 VAC
230 for 230 VAC
48 for -36 to -72 VDC
# Specify interface:
V35 for V.35 interface
X21 for X.21 interface
530 for RS-530 interface
V24 for V.24/RS-232 interface
G703 for G.703 Codirectional, card version
G703/TB for G.703 Codirectional, with terminal block (standalone)
G703/RJ for G.703 Codirectional, with RJ-45 (standalone)
Specify second, redundant power supply:
For ordering options, see main power supply.

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

& Specify connector:
V35/1 for adapting one modem card's 25 pin connector to one V.35, 34-pin connector
X21 for adapting two adjacent modem cards' 25-pin connectors to two X.21, 15-pin connectors





Table 1. Approximate Range

Data Rate 19 AWG 22 AWG 24 AWG 26 AWG
Kbps km miles km miles km miles km miles
768 1.8 1.1 1.2 0.7 1.0 0.6 0.8 0.5
512 2.5 1.5 2.0 1.2 1.5 1.0 1.0 0.6
384 4.5 2.8 3.0 1.8 2.5 1.5 2.0 1.2
256 6.0 3.8 4.5 2.8 3.5 2.0 3.0 1.8
192 6.5 4.0 5.0 3.0 4.0 2.5 3.0 1.8
128 9.0 5.5 6.5 4.0 5.0 3.0 3.5 2.0
64 11.5 7.0 7.5 4.5 5.5 3.5 3.5 2.0




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