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DC Powered Bell 202 / 202T and V.23 Modems

Applied Systems Engineering SM 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.

Rack Mount Bell 202 Modem

Bell 202 Modem - Box

These modems 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, 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 IED/RTU manufacturers, a low-cost "board only" version can mount directly in the Remote unit.

• Power
• Timing
• Levels
• Isolation
• LEDs
• Other
• Packaging
• Testing your modem
• Modem Part Numbers

 

Power

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)

Timing

Carrier detect on delay: 2 to 30 msec., 1 msec. increments

RTS/CTS delay: 0 to 254 msec., 2 msec. increments

Levels

Transmit Gain: 0 to –31 dB, 1dB increments

Receiver Gain: –35 or -45 dB

Isolation

1,500 VAC Telco

1,800 VAC Power Supply

LEDs

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

Other

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

Packaging

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

Metal enclosure is 187x105x36 mm (7.35x4.14x1.42”) and includes flanges with 4 mounting holes

“Board only” dimensions are 100x160mm (3.94x6.30”)

Testing your Bell 202 Modem

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:

Loop back Switch (SW2)

The loop back switch allows you to disconnect the analog output signals from the telephone line, and loop back the transmit and receive signal though a 10 dB pad. The 10 dB pad simulates a telephone line, and ensures the transmit signal does not override the receive signal. You can then transmit RS232 data on the transmit pin of the DB25 connector (pin-2), and the same RS232 data is received on pin-3 of the DB25 The loop back switch is located on the front panel of the Bell 202 modem enclosure.

The following steps describe the test procedure for the single-channel modem:

Connect the Bell 202 modem to a PC or laptop COM Port using a straight-through modem cable.

Run a terminal program such as Hyper terminal on Windows.

Set the terminal program to the appropriate communication port (for example, COM 1). Set the baud rate to 1200 bps, and set the Flow control to Hardware.

Place the Bell 202 modem in Loop back, by pushing in the Loop back switch.

Type a letter on the keyboard. You should see the letter displayed on the terminal screen. The ASE modem LED's (TX, RX, RTS, CTS, and CD) should flash when the keystroke is entered. The Power LED should always remain on.

This simple test verifies both the sending and receiving portion of the Bell 202 modem.

Modem Part Numbers