58 MDS™ Master Station MDS 05-6399A01, Rev. F
- Lo – The PTT line is active-low.
• Push To Talk Delay – Specifies a brief time delay after a keying event, which must
expire before the radio is allowed to transmit. The allowable range is 0 to 255 ms, with the
default being 0.
• Clear To Send Delay – Specifies a brief time delay between when an RTS (ready-to-
send) signal is received and when the CTS (clear-to-send) signal is returned. The
allowable range is 0 to 255 ms, and the default is 0.
• Automatic Freq. Correction – Automatic Frequency Correction, is used to counteract the
slight RF frequency drift that may occur over time or through wide swings of ambient
temperature. AFC should only be enabled when operating this device as a remote, as all
remotes in the system use AFC to track the master station frequency. Under normal
operation, the modem is capable of compensating for small frequency errors even with
this mode disabled. Enabling AFC further extends the frequency capture range when
operating with legacy hardware that may have significant frequency error.
• Switched Carrier B Modems – In some networks, the Master unit is not keyed
continuously (Ckeyed), and transmits only when it has data to send to Remotes. This is
known as Switched Carrier operation. The Switched Carrier setting is only for use with the
9600B modem (for compatibility with MDS x710 radios). In such networks, the Remote
radios should have the Switched Carrier setting turned ON. The default setting is OFF
which assumes B-modem operation with a continuously keyed Master. Ckey operation
only applies to Master units operating full-duplex and does not apply to legacy-packet or
packet with MAC modes. When operating continuously keyed, latency is decreased and
AFC operation on legacy remotes may be improved. Switched carrier operation, when low
latency is not required, is recommended when operating in high ambient conditions to
reduce power consumption and heating.
• Force DCD to Asserted – Some systems require a constant Data Carrier Detect (DCD)
signal. This setting allows the radio to be configured to provide a DCD signal without the
need for special cabling.
Enabling Force DCD to Asserted will cause the RX LED on the radio interface to
turn on, regardless of whether the radio is receiving data or not.
• Data Key Hold Time-out – When operating in data key mode, this parameter specifies
the number of character-times the transmitter will remain keyed for after the last character
it receives. For networks with the demand for a higher modem speed than the baud rate of
the serial port, this parameter can be adjusted from 1 to 10 characters. This parameter
gives the overall network better performance by preventing frequent key-up and key-down
sequences between characters. This only applies to networks with all SD radios.
• Simplex Mode – This controls whether or not the Master Station will be running in
simplex (switched carrier) or full duplex mode. When simplex is enabled, TX and RX are
switched onto a single RF interface. A Master Station without an internal duplexer with a
single antenna output must have simplex mode enabled.
• Dlink Mode (B Modems) – Legacy products that only support B-Modems do not have
support for Dlink. Newer products such as the MDS SD have the ability to support Dlink
even when using B-Modems. Depending on site-specific requirements, this value may
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