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RAD
ASM-24 Sync Short Range Modem |
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- The ASM-24, High Speed
Short Range Modem, operates synchronously at full or
half duplex, over unconditioned twisted pair, 4-wire
lines. It has a range of up to 26.4 km (16.5 miles),
depending upon the wire gauge and data rate used
(see Table 1). ASM-24 operates at data rates from 48
up to 144 kbps (48-128 kbps for V.24).
- The line code used,
PR4 (Partial Response, Class IV), reduces bandwidth
requirements, providing excellent performance and
long range.
- ASM-24 incorporates
interface circuits for the DTE, an automatic
equalizer, a modulator, a demodulator, and
diagnostics circuitry. It is coupled to the line
through isolation transformers which, in conjunction
with other circuitry, protect against AC or DC
overvoltages. The protection circuitry enables
operation even when DC is connected to the line.
- Transmit timing is
provided internally, or is derived externally from
the data terminal or receive signal. Receive timing
is derived from the line received signal.
- ASM-24 features V.54
diagnostic capabilities to perform local analog
loopback, and local and remote digital loopbacks.
The loops can be activated manually from the front
panel or via control signals from the digital
interface.
- A built-in Bit Error
Rate Tester (BERT) enables complete testing of both
modems and the line. A front-panel switch generates
a pseudo-random test pattern (511 bits) according to
ITU V.52, for testing end-to-end connectivity. When
a bit error is detected, the ERR LED flashes.
- ASM-24 is available as
a standalone unit or as a rack-mount card for the
ASM-MN-214 19" modem rack. The rack can carry
up to 14 cards and is supplied with 25-pin D-type
connectors.
- Optional rack mounting
hardware is available for mounting one or two
standalone units in a 19" modem rack.
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