SHORT HAUL MODEM (SHM-FSK)

8. RS-485 Interface

Optional RS-485 modules are available for connection to multiple remote devices. The following modules are available:

•RS-485 Module 2-Wire, part number MD3317

•RS-485 Module, 4-Wire, part number MD3318

All operating functions and instructions are the same as for the RS-232 full duplex version, except that the digital interface through the DB25 connector uses pin 12 as the -DO/RI connection and pin 13 as the +DO/RI connection. The RS-232 connections (pins 2, 3 and 7) are not functional.

CAUTION

Do not connect anything except an RS-485 signal to positions 12 and 13 on the DB25 or damage to the circuit could occur.

The AE-485 (Auto Enable) circuit contains a special feature that eliminates the need for a separate enable signal or line to command the 485 transmit and receive functions. Data will pass through the SHM-FSK’s

RS-485 port transparently in either direction. The SHM-FSKs are operated in full-duplex point-to-point mode (no carrier control) when using the AE-485 interface. Up to 32 remote RS-485 devices can be multi-dropped off the SHM- FSK AE-485 port at distances of up to 4000 feet and at data rates of 9600 baud. A 100-ohm termination resistor should be connected at the ends of the 485 line.

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Black Box MD3318, MD3317, ME840A-M, ME840A-S manual RS-485 Interface
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ME840A-M, ME840A-S, MD3318, MD3317, RS-485 specifications

The Black Box IC113C and IC175C are part of a series of versatile RS-485 interface converters designed to facilitate reliable data transmission over long distances. RS-485 is a standard defining the electrical characteristics of drivers and receivers for use in serial communications systems, and these specific Black Box converters exemplify the technology's adaptability and robustness.

The IC113C is an RS-485 to RS-232 converter, providing a seamless transition between these two common serial communication protocols. With a compact design, it boasts an operating temperature range of -40 to 85 degrees Celsius, making it suitable for harsh environmental conditions. Its key feature includes the ability to extend the communication distance up to 4,000 feet, which is ideal for industrial applications where devices may be far apart. Additionally, the IC113C includes built-in surge protection, ensuring that the device can withstand electrical noise and spikes, ultimately increasing the system's reliability.

On the other hand, the Black Box IC175C serves as an RS-485 to USB converter, bridging older serial devices with modern USB interfaces. This converter is critical for users wanting to connect legacy equipment to contemporary computing systems. Featuring a plug-and-play design, the IC175C is easy to install with no external power supply required, as it is powered directly through the USB connection. It also supports data rates up to 115.2 Kbps, ensuring fast and efficient data transfer.

Both models employ differential signaling, which enhances noise immunity and allows for greater transmission distances compared to single-ended communication standards. Furthermore, the converters support multiple nodes on the same bus, accommodating a network of devices without requiring complex wiring schemes.

In summary, the Black Box IC113C and IC175C offer essential features that cater to diverse industrial and commercial applications. With their robust construction, extensive operating ranges, and compatibility with various communication protocols, these converters enhance system interoperability and provide durable solutions for long-distance data communication needs. Whether connecting legacy systems or extending communication capabilities, these devices exemplify reliability and efficiency in modern data transmission technologies.
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