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メディア・コンバーター Dataforth SCM9B-A2000 SeriesのPDF ユーザーマニュアルをオンラインで閲覧またはダウンロードできます。Dataforth SCM9B-A2000 Series 8 ページ。 Converter boxes

SCM9B-A1000 & SCM9B-A2000 USERS MANUAL 2

GENERAL DESCRIPTION

The SCM9B-A1000 and SCM9B-A2000 series converter boxes convert

RS-232 communications signal levels to the correct electrical signals

required by RS-485. The RS-485

communications

standard is

recommended when many DATAFORTH modules, or other addressable

devices, must be connected to a host computer over long distances. The

SCM9B-A1000 and SCM9B-A2000 converters allow communications

bus lengths up to 4,000 feet and baud rates up to 115K baud using one

twisted pair of wires.

The RS-485 communications standard is half-duplex, therefore data can

be transmitted in only one direction at a time. The SCM9B-A1000 and

SCM9B-A2000 automatically control the bus direction without external

handshaking signals from the host. Therefore, host software written for

RS-232 may be used without modification. RS-485 bus control is

completely transparent to the user.

The SCM9B-A1000 and SCM9B-A2000 can also operate as RS-485

repeaters. Repeaters are required to extend communications bus

lengths or allow more than 32 RS-485 devices to be connected to a

communications bus. A repeater simply reamplifies, or boosts, existing

RS-485 signals transmitted over long distances.

The SCM9B-A1000 converter boxes are powered by either 115Vac or

230Vac and contain an internal +24-volt 1A power supply for powering

DATAFORTH modules. The SCM9B-A1000 power supply is protected

against overloads and short circuits. The internal power supply may be

used to power accessory circuits such as relays or 4-20mA transmitters.

The SCM9B-A2000 converter boxes operate on a wide range of power

supply input voltage:+10 to +30Vdc unregulated.