B202 - SCADAmetrics

B202 - SCADAmetrics
Bell 202 Modem
Standards-Based, Non-Proprietary Modem
For Radio Telemetry…
The SCADAmetrics Model B202 Modem is designed to
provide non-proprietary, Bell-202 data modulation and
demodulation for many popular analog telemetry
The unit offers the following notable features:
● Wide-Input Power Range 10-30VDC.
● Computer/PLC/RTU Interface: RS-232/DB9F.
● MODBUS- and DF1-Compatible
● Radio Interface: RJ45F.
● Industrial Din-Rail Mount.
● LED’s: Power, Transmit, Receive, TxD, RxD.
The B202 modem permits users to mix various makes
and models of compatible radios within a telemetry
system, thereby alleviating the problem of vendorlockin.
This new design is based upon the MX614 modem IC
(CML Micro), and it is also fully compatible with legacy
Bell-202 modems that are based upon the TCM3105
modem IC (Texas Instruments), such as the Calamp
DM-3282, Maxon SD-FSK, and Paccomm UAS-1200 &
HT-1200A. Compatibility is anticipated with a wide
range of popular analog telemetry radios, including
models from the following manufacturers:
● Tecnet / Maxon
● Ritron
● GE / Microwave Data Systems
● Calamp
● RF Neulink
● Adjustable Transmit Audio Level.
● Selectable RF or Modem Carrier Detect.
● Carrier-Detect Byte Filtering Option.
● Receive Signal Equalizer Option.
● ‘Dumb’ Mode Operation.
St. Louis, Missouri USA
Manufacturing Location:
Relative Humidity:
Panel Mounts:
Supply Voltage/Power:
Supply Current:
Term. Blk. Conductors:
Internal Power Efficiency:
Circuit Protection:
Serial Communications
Interface Port:
Protocol Compatibility:
Radio Communications
Modulation Type:
Interface Port:
4.125” x 3.250” x 1.750”
3.8 Ounces
-30C to +85C
5% to 95%, Non-Condensing
Two (2) Universal Din-Rail Clips
10VDC to 30VDC, 0.50W max
42mA @ 12VDC, Typical
84mA @ 24VDC, Typical
16AWG Max, 26AWG Min
90%, Typical
Fused (375mA) + TVSS Diode +
Reverse-Polarity Protection Diode
● Is the B202 a ‘smart’ modem? No, the B202
modem is a ‘dumb’ modem. The benefits are total
control of the modulation and demodulation process
and enhanced ability to troubleshoot. However a
‘dumb’ modem requires the user to key the
transmitter through software prior to and during data
transmission using the RTS serial port pin. The user
also must provide logic to detect and separate valid
packets from extraneous noise. This is typically done
by framing each packet with a pre-determined byte
What are the power requirements of the
B202? The B202 provides the user with a great deal
of flexibility in that it will operate on any voltage
between 10-30VDC. However, it is almost always
preferable that the user power the modem with the
same voltage source that is used to power the radio –
which will generally be ~12VDC. Pin 8 of the RJ45
jack provides a direct connection back to the V+
terminal block. If the radio is to be powered with a
separate voltage source, then it is imperative that Pin
8 of the RJ45 jack should not be connected to the
RS-232C (DB9F Jack, DCE):
1: DCD (Transmitted to DTE)
2: TxD (Transmitted to DTE)
3: RxD (Received from DTE)
4: N/C
5: GND
6: N/C
7: CTS (RTS from DTE)
8: N/C
9: N/C
300 to 1200 bps
None (Requires External RTS/PTT Control)
Custom Binary & ASCII Protocols
AFSK (Audio Frequency Shift Key), Bell-202
1: TxAudio (Adj: 0-1 Vpp / 0-0.354 Vrms)
2: RxAudio
3: PTT (Active Low)
4: Channel Busy
5: Ground
6: N/C
7: N/C
8: DC Power
(Non-Fused, Mapped from V+ Terminal)
Configuration Jumpers
Radio Channel Busy Normal (~5V=BUSY) JP1 = NORM
Radio Channel Busy Inverted (0V=BUSY) JP1 = INV
(Sets Polarity of Radio Channel Busy/Carrier Detect)
DCD Source = Radio Ch. Busy
DCD Source = Modem Energy Detect
(Sets The Source Of DCD Signal: Radio or Modem)
DCD Byte Filter ON
JP3 = ON
DCD Byte Filter OFF
(Filter ON: Data Only Passed Thru When DCD Asserted)
Receive Equalizer ON
JP4 = ON
Receive Equalizer OFF
(See Explanation On Page 6 of MX614 Datasheet)
● Does the B202 require programming? No, the
unit features 4 jumpers for tailoring the modem to
your radio and application, and one trim pot for
adjusting the transmit audio level.
● Do you offer radio interface cables? Yes.
Because many of the popular telemetry radios feature
DB9, DB25, or DB15 interface ports; and it’s now
extremely easy and popular to create custom cable
assemblies with RJ45F-to-DSub Adapters. This allows
us to offer cable assemblies for many popular
telemetry radios.
Our cable assemblies generally
consist of an RJ45F-DSub Adapter and a premium
shielded CAT5 patch cable (24-gauge, solid-copper
● What documentation is available? The B202 is
offered as a non-proprietary modem device whose
operation can be troubleshot and repaired by qualified
technical personnel. For this reason, complete
documentation is provided – including an operations
manual, schematics, and the modem IC datasheet.
● What are the Bell-202 modulation tones? The
Bell-202 standard uses 1200 Hz for ‘MARK’ (Binary
‘1’), and 2200 Hz for ‘SPACE’ (Binary ‘0’).
St. Louis, Missouri USA
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