Bell 202 Modems for SCADA

Bell 202 Modems for SCADA

ASE’s DM series products are Bell 202 /202T and V.23 modems designed for operation over leased line communication circuits as commonly used in the electrical power and pipeline SCADA industries.
These modems for SCADA have been designed with many commonly requested features, including 900Hz soft-carrier turnoff, LED indicators, digital control over most timing parameters (in 1-millisecond increments), transmit levels from 0 to-31db, a PTT (Push to Talk) circuit, and input power from 5 to 160 VDC. The primary modem circuitry is based on commercially available ICs with many years of field-proven operation.
All Bell modems are available in a 19″ rack configuration with a 16-slot custom backplane or packaged in a metal box. For OEM manufacturers, a low-cost “board only” version can be mounted directly on the remote terminal unit or IED.


19” rack is 5 1⁄4” high with slots for 16 modems plus redundant power supplies

Metal enclosure is 187x105x36 mm (7.35×4.14×1.42”) and includes flanges with 4 mounting holes

“Board only” dimensions are 100x160mm (3.94×6.30”)



  • Box modem: 5 to 160 VDC, draws less than 500 mw
  • Rack Modems: 120/240 VAC to power supply
  • “Hot Card Swap” on rack mount configuration (backplane supports dual power supplies)


  • Carrier detect on delay: 2 to 30 msec., 1 msec. increments
  • RTS/CTS delay: 0 to 254 msec., 2 msec. increments


  • Transmit Gain: 0 to –31 dB, 1dB increments
  • Receiver Gain: –35 or -45 dB


  • 1,500 VAC Telco
  • 1,800 VAC Power Supply


  • Transmit (TD) and receive (RD) data, RTS, CTS, carrier detect (CD), and power
  • Connections
  • Analog side via 4-wire RJ-11 (box modem) or terminal screws (rack mount modem)
  • Digital side via DB-25 RS-232


  • 2-wire or 4-wire (2-wire with optional 156 msec. receiver squelch)
  • Constant or switched carrier
  • 900Hz carrier turnoff (Bell 202 modem only), 1 – 15 msec, 1 msec. increments

Your Bell 202 modem comes fully tested from the factory. However if you need to perform some tests on an installed modem, please follow the steps below to verify modems operation:

TELCO Loop Back Switch (SW4)

SW4 is an external switch. If ON, data received on the analog TELCO side will be looped back to the TELCO transmitter. In this mode, the digital (RS-232) side is disabled

Modem Part Numbers

ASE Modem Part Numbers
Standalone Bell-202/V.23modem in metal enclosure, operates at 12 to 160 VDC
Rack-mount Bell-202/V.23modem for operation in ASE 19” modem rack, SM-RACK-16
19” Rack-mount chassis with slots for 16 DM-FSK-X-V modems. Includes one AC/5V power supply
Redundant power supply for SM-RACK-16

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