The DGH A1000 and A2000 series converter boxes convert RS-232
communications signal levels to the correct electrical signals required by RS-485.
RS-485 is recommended when many DGH modules, or other addressable
devices, must be connected to a host computer over long distances. The A1000 and A2000
converters allow communications bus lengths up to 4,000 feet and baud rates up
baud using one twisted pair of wires.
RS-485 allows bi-directional data on the same pair of wires,
therefore some means of arbitrating the data direction is required. The A1000 and
A2000 converters automatically control the bus direction without the need for external
handshaking signals from the host computer. Therefore, host software written for
half-duplex RS-232 may be used without modification. The RS-485 bus control is completely
transparent to the user.
The A1000 and A2000 can also operate as repeaters for RS-485. RS-485
repeaters are required to extend communications bus lengths or allow more than 32 devices
to be connected to a communications bus.
The A1000 converters are powered by either 115Vac or 230Vac. The A2000
converters operate on a wide range of power supply input voltage: unregulated +10 to
A2400 is an RS-232/RS-485 converter designed to interface all DGH RS-485
products to radio and leased telephone line modems. Many radio and leased line
modems require an RS-232 signal to activate, or "key-up", the
transmitter. They also require adequate time for the transmitter to turn on
before transmitting any data. This transmitter turn-on delay time mandates that
the data be delayed while the transmitter is turning on. The amount of delay
time required varies between modem types and manufacturers.