CrosStar MD-201 Bell 202 Modem With DF1 To HDLC Protocol Converter
 
The CrosStar MD-201 Modem is a half-duplex Frequency-Shift-Keyed (FSK) audio tone modem with integral protocol converter.
 
The MD-201 Modem operates at 1200 baud on private leased telephone lines, voice/audio radio links, or any dedicated two wire circuit. The MD-201 has dual isolated audio ports plus a radio Push-To-Talk (PTT) output, so it can operate both telephone and radio circuits simultaneously, providing active audio mixing to prevent impedance mismatching. Both two-wire and four-wire telephone circuits can be interfaced easily to the modem. A Modified HDLC protocol is used over the audio link which interfaces to several legacy telemetry systems. The MD-201 can operate as either the telemetry master or remote.
 
SCADA equipment connects to the MD-201 Modem by an RS-232 Data Communications Equipment (DCE) 9-Pin Connector. Data is exchanged at 9600 baud using Allen-Bradley's DF1 protocol.
 
The MD-201 Modem has ten colored LED lights on the front panel displaying the status of both the HDLC Modem and the RS-232 DF1 signals. Three connectors on the rear panel provide interconnection for the power input and radio terminals, a telephone line modular jack, and the RS-232 DCE connection. Internal controls are provided to adjust the audio level on the radio connector, and to select the operational mode of the protocol converter.
 
Suggested uses for the MD-201 Modem include interfacing newer SCADA computer equipment to legacy radio/private leased telephone line based telemetry systems, and integrating remote PLCs in to legacy telemetry systems.
 
 
 
Features
 
Single 12V Power Requirements.
Provides Protocol Conversion between Allen-Bradley DF-1 and Modified HDLC.
ABS plastic enclosure.
Compatible with both Dedicated Telephone lines and Radio Systems.
Easily works with both two-wire and four-wire telephone circuits.
Signal Status lights on front panel.
Simple installation, no jumpers.
Radio audio adjustments provided.
Extends the Operational Lifespan of Legacy Telemetry Systems.
 
 
Specifications
Electrical
 
Supply Voltage:
10 to 24 VDC, 12 V Recommended
Supply Current:
140 MilliAmps
 
 
Indicators
 
Front Panel:
Four HDLC Modem Status LEDs:
 
    TX On- Transmit On, Red
 
    TD- Transmit Data, Green
 
    CD- Carrier Detected, Yellow
 
    RD- Received Data, Red
 
 
 
Six DF1 Interface Status LEDs:
 
    FLT - DF1 Message Fault, Red
 
    RPT - Remote Being Repeated, Yellow
 
    RTS - RS-232 Request To Send, Green
 
    TX - RS-232 Transmit Data, Red
 
    RX - RS-232 Receive Data, Red
 
    DF - Remote Data Failed, Yellow
 
 
Communications: Modem
 
Baud Rate:
1200BPS Half-Duplex.
Protocol:
Modified HDLC with NRZ.
 
Selectable Between Telemetry Master and Telemetry Remote Operations via Internal Switch.
Tone Frequencies:
Mark: 1200 Hz  Space:  2200 Hz
Phone Line:
Two-Wire or Four-Wire, RJ-11 jack.
Line Level:
0 dBm, 600 ohms, Matches 150 to 900 ohm Dedicated Telephone Lines.
Radio Terminal:
7 Pin P1uggable Connector.
Radio Speaker Input:
4 to 50 ohm, Voltage Isolated.
Radio Mic Output:
-45 to -8 dBm, Adjustable with Internal Control.
Radio PTT Output:
Open Collector 60VDC Transistor, Controlled by RTS.
 
 
Communications: RS-232
 
RS-232 Connector:
DB-9F configured as DCE (modem) provides TXD, RXD, RTS, DSR, CTS, & CD Signals.
Baud Rate:
9600BPS Full-Duplex Eight Bit Data, One Stop Bit, No Parity.
Protocol:
Allen-Bradley DF-1 for PLC-5 Full Duplex with BCC Error Detection.
 
 
Physical
 
Size:
5.5 W x 2.0 H x 5.375 D inches.
Weight:
14 oz.
Temperature:
0 to 65° C.
Humidity:
10 to 90%, Non-condensing.
Enclosure:
ABS Plastic Desktop Style, Optional Chassis Mount Available.
 
 
 
Documents
 
MD-201 Modem Data Sheet in .pdf format
 
 
Made In the United States of America.
 
© Copyright 2005 CrosStar, LLC.  All Rights Reserved.