User`s manual

81
CHAPTER 3 COMMUNICATIONS BY THE MODEM FUNCTION
3
3.2 System Configuration
(6) Connectable lines
(a) The connections can be made with the following lines.
Perform connection tests beforehand and confirm that connection is possible.
• Public line or office telephone system of analog two-line method
• Digital line (ISDN)
(b) It is not possible to connect to call-waiting lines, in order to avoid data errors or
automatic line disconnection due to the call-waiting interrupt tone.
(c) Avoid connections with party-line telephones to avoid interrupted calls during
communication.
(d) If an alert sound is sent at fixed intervals from the communication machine to
prevent long-term calls, data may experience errors.
It is recommended to check the normality/abnormality of data reception between devices, and perform
transmission-retry processing when an abnormality is detected.
(e) See the modem/TA manual regarding the connection from a modem to public
line/office telephone system, or from a TA (terminal adapter) to a digital line.
(7) Communication system
Communication via the modem function is performed using full-duplex communication.
Connections cannot be made devices designed for half-duplex communication.
(8) Data communication and notification to external devices
(a) Data communication with external devices and notification to a pager receiver are
performed using the public line or electric wave transmitted from the electric wave
transmission base.
There might occur a condition in which correct data communication or notification cannot be carried out due to
an error from the system's setup environment, electric-wave transmission status, error in the partner device,
etc. Perform connection tests beforehand and confirm that connection is possible.
(b) In notification processing via electric-wave transmission, errors from the pager
receiver cannot be detected. Setup a separate call circuit with a lamp display or
buzzer to ensure the safety of the programmable controller system.