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3.4.4 External Modem
The internal NEMA Port 3 connector described earlier transmits and receives data
via an internal 1200 bps modem, per the NEMA TS-2 specification. If some other
communications medium is desired, such as fiber, radio or high-speed twisted
pair, an external modem may be attached to the Port 2 EIA-232 connector. In
addition to TxD and RxD, Port 2 provides the Request to Send (RTS) and Clear to
Send (CTS) signals required by many external modems. Typically, the RTS line will
be unasserted while the EPAC "listens" to the incoming data on the RxD line. If the
incoming message requires a response, the EPAC will assert RTS, which reverses
the external modem from Receiver to Transmitter. After allowing a period of time
for the modem at the other end to "lock" onto the signal, the external modem
asserts CTS as an input to the EPAC, which begins the data flow from the EPAC to
the external device on the TxD line. Once finished transmitting, RTS is unasserted,
external modem CTS goes away, and EPAC "listens" for the next data packet.
3.4.5 Infrared Port
The EPAC300-M50 Series includes a wireless infrared port compatible with the
Microsoft Windows for Pocket PC RAW IR protocol. This protocol is included in
most Windows laptop personal computers and personal digital assistants (PDA).
This port works exactly like the NEMA EIA-232 Port 2, but without need for a cable.
The transmission medium is a modulated light beam. The light beam is infrared,
meaning it is outside the visible color range detected by the human eye. The light
transmission is similar to a standard television remote control, meaning that its
light emission power is safe to the human eye. As with a TV remote control, the
transmitting device must be used within the line of sight, aimed towards the
controller red window, and located within approximately six feet. The window must
be clean.
Note that the infrared port replicates the 25-pin "D" NEMA Port 2
connector described earlier in this manual. When using a PDA or laptop computer,
the IR port of that device must be configured (bit rate, data length, stop bits, parity)
in the normal fashion for NEMA Port 2, except the device must communicate via IR,
as opposed to EIA-232. For example, Pocket ACTRA communicates via an EIA-232
cable using the Windows COM1 on the PDA, or communicates via IR using the
Windows COM2 on the PDA. When using IR of devices other than Pocket ACTRA,
please consult the manual for that device to configure the serial port for Windows
RAW IR protocol. Also note that many devices default to other IR protocols. Be
sure to check the Windows IR configuration screen to turn OFF the default
protocol. For example, the Windows for Pocket PC default is defeated as follows:
START
SETTINGS
CONNECTIONS
CONFIGURATION
BEAM
"Receive all incoming beams and select discoverable mode"
AUGUST 2005
EPAC300-M50 SERIES USER'S MANUAL
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