4xx Preliminary Generic User Guide. 4 Jan 06
10
Load Compensation
Normally this is set to 600 Ohm to match the line impedance.
Switching to High increases the gain of the receiver and is only used when the
receive signal is so low it causes data errors.
KOD Function
Data is used to key the modem On and Off when there is no RTS handshaking
from an attached device.
KOD Direction
The KOD direction can be reversed and FSK can raise RTS at the modems
data port.
KOD Delay
The time between the KOD generated RTS and when data occurs, note the
same period of time occurs after data ceases to when RTS is lowered.
Selectable time periods are 1.6, 3.3, 6.6 and 13ms.
Anti- Streaming
Anti streaming is a feature that prevents a modem connected to a
malfunctioning controller from monopolizing and jamming up the
communications path.
As an example, in multi-drop, polled, environments a “Master” sends out a
logical address and expects a response from the addressed device. If another
unaddressed controller has raised RTS, this will cause its attached modem to
broadcast a carrier tone which will “jam” all the modems on the line.
The Ant-Streaming feature of the modem prevents this by limiting the amount
of time that the modem can continuously transmit to around 7 seconds. If
Request To Send remains continuously active for longer than this period, the
modem will override the condition, and stop transmitting until RTS goes Low.
External KOD On/Off Pin 9
Disconnects Pin 9 to prevent potential conflict with controller RS232 Port
Data Protocol
RS232
This is the standard format for the modem and is designed for short distance
communications of less than 100ft and is ideal when connecting to the traffic
controller or other devices within the cabinet.
RS422/485
is used to drive longer distances than RS232 over 2 pairs of
balanced transmission lines; this is an option and must be specified at the time
of order.
