Black Box Short-Haul Modem B, ME810, ME800A-R2, ME805-C-R2 manual Flow Control

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SHM-B ASYNC

3.4 Flow Control

The SHM-B uses a clever, yet simple way to allow this unit to work with a broad line of equipment.

STANDARD EIA-232C HANDSHAKING (RTS/DTR CONTROL

JUMPER IN EN POSITION)

The individual SHM-B modems force their own DTR, RTS, CTS, and DSR control lines HIGH (>+3V) when:

The twisted-pair wires are installed correctly.

Power is applied to both modems.

No computer devices are attached to the modems.

This forces DCD HIGH on the remote modem; thus, the remote modem knows to expect data. In this state, “all systems are go.” The only way this state changes is if your equipment overrides this condition. For example, if your equipment drops DTR to a NEGATIVE signal, your equipment’s DTR being low will override the SHM-B’s DTR, and DCD on the remote modem will go LOW.

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Contents Short-Haul Modem B SHM-B Async SHM-B Async SHM-B Async SHM-B Async Trademarks Used in this Manual Distance miles/km SpecificationsOperating Temperature 32 to 112F 0 to 50C SHM-B Async Introduction Four-Wire Connections InstallationSHM-B board 5-screw terminal block EIA-232 Connection Wiring diagram for two SHM-B unitsEIA-232 Pin Connections on SHM-B Switch SettingsPinning with DTE/DCE switch in the DCE position Flow Control ON/X-OFF Mode Operation Activating the Loopback switchSHM-B Async Rackmount Installation SHM-B Async Troubleshooting Guide SHM-B Async SHM-B Async SHM-B Async SHM-B Async SHM-B Async Copyright 2000. Black Box Corporation. All rights reserved