VEGA Phoenix PSI Data Fax Modem - Manual (Page 64)

PSI-DATA/FAX-MODEM/RS232
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Echo If the echo is on, all characters sent by the PC in command mode are sent back by
the modem. The characters can thus be displayed on-screen on the PC.
DCD Signal When the partner carrier detect signal is detected, the RS-232 interface activates
the DCD signal (Data Carrier Detect). Alternatively, this signal can also be
permanently switched on.
DSR Signal The DSR signal (Data Set Ready) of the RS-232 interface can be permanently
switched on or switched off in command mode.
DTR Signal Your modem can process the DTR signal (Data Terminal Ready) as follows:
– The modem returns to command mode if there is no DTR signal at the RS-232
interface.
– The modem hangs up and returns to command mode if there is no DTR signal
at the RS-232 interface.
– The modem hangs up, is reset, and returns to command mode if there is no
DTR signal at the RS-232 interface.
– The modem ignores the DTR signal. This may be necessary when using a
PLC, as the RS-232 interface of a PLC is often unable to provide a DTR signal.
Flow Control The data flow control of the RS-232 interface can be set for various operating
modes:
– For the "Hardware" setting, the CTS and RTS signals are used for a
bidirectional data flow control.
– For the "Software" setting, the data flow control is bidirectional using XON and
XOFF characters.
– In "XON/XOFF Unidirect" mode, the XON character is sent to the PC (DTE) to
start data transmission and the XOFF character is sent to stop data
transmission. The PSI-DATA/FAX-MODEM/RS232 ignores XON and XOFF
characters sent by the PC.
– Data flow control can also be switched off completely. This may be necessary
when protocols such as 3964R are transmitted, which control the flow
independently.
Compression Data compression on the telecommunications cable results in increased data
throughput.
Modulation Method You can specify the transmission method of your modem (default: CCITT).
Table 6-1 on page 6-28 shows how the various settings work.