SHORT HAUL MODEM (SHM-FSK)

5.3 Receiver Gain

The SHM-FSK incorporates a receiver amplifier on the circuit board. This amplifier has low, normal, and high gain settings configured by a “T” shaped pin block near the center of the circuit board with pins marked “G1/H,” “G2,” “G3/L,” and “N” (the leg of the “T”). G1/H-G2 is the high-gain setting; G2-N, the normal medium gain; and G3/L-G2, the low gain. The units are delivered from the factory set at normal gain because the transmitter has been factory-set at normal output. If the data line is under 5000 feet long, the low-gain setting should be used whenever the high- power transmitter option is selected.

5.4 Carrier Detect:

Carrier Detect to the RS-232 connector is enabled or disabled by Jumper Matrix P3. The SHM-FSK units are shipped with the Carrier Detect enabled (jumper on).

5.5 Chassis Ground

Chassis ground can be connected to signal ground via Jumper P5. This is generally not recommended. A separate chassis ground wire may be connected to the SHM-FSK’s metal enclosure by means of any of the cover mounting screws as desired to avoid a possible shock hazard.

5.6 Half-Duplex Operation/Carrier Control

The SHM-FSK can be operated in multi-drop/half-duplex mode by controlling the transmitter’s carrier on/off using external signals. The most common external carrier-control signal is through the RS-232 port RTS line (pin 4). This line are selected by Jumper P4, A-B. When an external RTS logic high is asserted, the SHM-FSK carrier is turned on; logic low or ground turns the carrier off. The SHM-FSK RTS line is biased low, so that if the RS-232 cable is disconnected or the external controlling device is turned off, the carrier will go off. A-B selects RTS and B-C selects DSR. Usually only the Remote units have their carriers controlled by the devices they are connected to. The Master unit’s carrier is left on all the time. (There is no interference, since the Master and Remote carrier frequencies are different.)

The factory setting for both SHM-FSK Masters and Remotes is P4, A-B, for full- or half-duplex point-to-point operation.

An alternative carrier-control method is to connect a cable to the SW1 header, which allows external contact closure or solid-state switch control of the transmitter. Please call technical support for special instructions.

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Black Box MD3317, RS-485, ME840A-M Receiver Gain, Carrier Detect, Chassis Ground, Half-Duplex Operation/Carrier Control
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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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