GE MDS Master Station Technical Manual page 65

setting. A possible exception is when the transceiver is inter-working with certain
early-generation MDS radio equipment.
Push to Talk Signal – Specifies the sensing polarity of the PTT line. This must be
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configured to one of the following values:
- Off – PTT line is not used.
- Hi – The PTT line is active-high.
- Lo – The PTT line is active-low.
Push To Talk Delay – Specifies a brief time delay after a keying event, which must
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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
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(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
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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
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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 on
radio modems with "B" suffixes (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 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)
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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
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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 then the baud rate,
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.
MDS 05-6399A01, Rev. E MDS™ Master Station 61