Jim Mimlitz

Jim Mimlitz, SCADAmetrics

SCADAmetrics® is pleased to introduce a new member of our DINstrumentation series – the Smart Bell 202 Modem! The Model SB.202 Modem delivers non-proprietary, Bell-202 data modulation and demodulation for many popular analog telemetry radios. Its rugged design is optimized for use with industrial serial communication protocols, such as
Modbus/RTU, Allen-Bradley DF1, and DNP3.

‘Smart Bell-202 Modem’. Model SB202.

Non-proprietary, Bell-202 modem technology offers significant advantages when applied to certain difficult system integration projects: 1. When combined with licensed VHF and UHF FM radios, it offers unsurpassed ability to punch through dense foliage and communicate across long distances with imperfect line-of-sight. 2. It permits interoperability of a mix of various makes and models of compatible FM radios within a telemetry system.

In 2012, we introduced a basic, ‘dumb’ Bell-202 modem module for radio telemetry applications. These legacy modems successfully served as drop-in replacements for the popular Calamp DM-3282 modem in the water, wastewater, oil, and natural gas industries throughout the United States, Canada, the Middle East, and Europe for almost a decade.

Legacy Bell-202 OEM Modem Module.
Model B202.

However, the setup of legacy ‘dumb’ modems have traditionally posed challenges to the user. The most demanding tasks are 1. implementation of radio “push-to-talk” pre-transmit and post-transmit timings; and 2. implementation of a delay in the transmit data stream until a sufficient duration of pre-transmit “push-to-talk” has completed.

In the past, push-to-talk timing and transmit data buffering has been achieved by setting up the serial port of the RTU or PLC for hardware flow control, and using the modem’s delayed RTS/CTS handshake to achieve proper pre-transmit and post-transmit keying of the radio transmitter.

Sound a little tricky? It used to be — Until Now!

SCADAmetrics’ Model SB.202 delivers all the benefits of Bell-202 modem technology – yet without the hassles. At the heart of the SB.202 is an intelligent microcontroller that supervises the timing of the radio’s transmit data stream, thereby allowing your RTU/PLC to offload its Modbus requests and responses immediately – without RTS/CTS delays. In fact, you may even set up your PLC for simple 3-wire serial communication with RTS/CTS flow control disabled. The SB.202 then intelligently handles the keying/unkeying of the radio using dip-switch-selectable timings. It is noteworthy that the Model SB.202 does not modify the content of the messages, and it does not add proprietary framing layers to the transmissions. Therefore, you may be assured that it will be over-the-air compatible with other-brand modems that adhere to the Bell-202 standard.

The Smart Bell-202 Modem – Front & Back Views.

For example, if your SCADA network’s communication system is built around the Schneider Electric™ SCADAPack 5902 Bell-202 modem and FM radio, then you can be assured that the SB.202 will interoperate seamlessly.


The SB.202 is Compatible with the Schneider SCADAPack 5902 Modem and SCADAmetrics EM-100 EtherMeter®.

SB.202 Modem Installed as a Drop-In Replacement for Schneider 5902 SCADAPack Modem. Note the SCADAPack Model 334 RTU (left) and Motorola XPR2500 VHF/FM Radio (right) .

The SB.202 is Compatible with Allen Bradley MicroLogix and C*Logix Controllers.

Download PDF Datasheet / User Manual Here: Smart Bell-202 Modem

Are you interested in how SCADAmetrics modem technology can help your SCADA system communicate more effectively through rugged terrain? Give us a call! We’ll be glad to discuss the details!

Jim Mimlitz

About Jim Mimlitz

Licensed Professional Electrical Engineer @ SCADAmetrics. Specialties: Connecting Flow Meters with SCADA, Telemetry, and Building Automation Systems. Electronic Circuit Design, Software Development.

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