RAD FCD-1L T1 or Fractional T1 CSU/DSU 

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FCD-1L T1 or Fractional T1 CSU/DSU

RAD FCD-1L T1 or Fractional T1 CSU/DSU 
FCD-1L/115     FCD-1L/230    FCD-1L/48     FCD-1L/R

  • The FCD-1L is a low-cost, single port CSU/DSU for T1 or Fractional T1 services. The DTE port is selectable for any data rate multiple of 56 or 64 kbps up to 1536 kbps. User data is placed into a T1 frame, using only the selected number of timeslots.
  • Timeslot assignment is according to the data port speed and is consecutive starting from any timeslot.
  • The FCD-1L T1 interface is compatible with carrier provided T1 services, including ASDS from AT&T, meeting all requirements of TR-62421. It supports both D4 and ESF framed formats. Zero suppression over the line is selectable for either Transparent, B7ZS or B8ZS. The integral CSU ensures a range of up to 1 mile.
  • The main T1 link may be clocked from the T1 network recovered clock, from the DTE or from an internal oscillator. The DTE port interface is internally selectable for V.35, RS-530/422. The physical connector is 25 pin D-type female. Special adapter cables can be ordered separately for X.21 and RS-449/422 (see Ordering).
  • Setup and control of the FCD-1L is by internal jumpers. Front panel switches control all diagnostics options. Maintenance capabilities include user activated local loopbacks at the main T1 link and DTE port.
  • The FCD-1L responds to network activated loops (RLB, LLB). The DTE port can respond to an in-band ANSI FT1 loop code that can be generated from the remote FCD-1L DTE port. A pseudo-random data pattern (BERT) can be transmitted for diagnosing the T1 link.
  • The FCD-1L displays two alarm types on front panel: major alarm and minor alarm. The alarms are displayed by front panel LEDs which can be reset by front panel switch. The FCD-1L has a Severely Errored Second indicator (SES). This indicator is ON when the Bit Error Rate (BER) on the T1 line is above 1 x 10-3.
  • When operating in the ESF format, T1 network statistics are stored in memory in compliance with the ANSI version. This information may be retrieved by the service supplier.
  • The FCD-1L is available as a stand-alone unit or as a card for the 19" rack that can accommodate up to 14 cards (ASM-MN-214). A rack mount adapter kit (RM-9) enables installation of one or two stand alone units in a 19" rack.


  • T1 or Fractional T1 CSU/DSU
  • Supports one DTE port
  • Selectable sync data rates of n x 56 or n x 64 kbps, up to 1536 kbps
  • DTE interface: V.35, RS-530, RS-449/422 or X.21
  • Framing format: D4, ESF, Unframed
  • Zero suppression: B7ZS, B8ZS, Transparent
  • T1 interface: complies with AT&T TR62411, TR62421, ANSI T1.403
  • Performance monitoring according to ANSI T1.403 (ESF mode only)
  • Unframed over T1

T1 or Fractional T1 CSU/DSU, stand-alone version

T1 or Fractional T1 CSU/DSU, card version for ASM-MN-214

* Specify power supply
230 for 230 VAC
115 for 115 VAC
48 for -48 VDC
24 for 24 VDC

Adapter cable for RS-449/V.36 36-pin connector

Adapter cable for X.21 15-pin connector

Adapter cable for V.35 34-pin connector






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