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2.0 PRODUCT DESCRIPTION
The GE MDS TD220MAX is a 25-Watt 220 MHz GMSK data radio intended for bridging messages over
the air between locomotives and wayside devices in rail applications or between ship and shore in
maritime applications. The data interface is Ethernet and uses the UDP/IP-based Simple
Timeslot/Frequency/Power Protocol (STFP), defined elsewhere. STFP can support various payload
protocols.
A time division channel access method is used by the TD220MAX for wireless communication. Each
second is divided into 8, 133-byte time slots. The radio further defines a multi-second epoch to allow the
effective number of time slots to be scaled according to system design. All radios in a system must be
configured with the same epoch size.
Precise synchronization of timing amongst radios is necessary for operation. Each radio can be
configured to use one of three timing sources: GPS, Precision Time Protocol (PTP), and over-the-air
(OTA). While system design can be flexible, a base radio installation typically uses either GPS or PTP
timing and a mobile radio typically uses OTA to synchronize to the wireless transmissions of a base radio.
Radios configured for GPS timing must be connected to an external GPS unit to receive NMEA sentence
information and the PPS signal. Radios configured for PTP timing will interact with a PTP Grandmaster
Clock over the Ethernet port using IEEE 1588 (PTPv2). Radios configured for OTA timing use messages
received wirelessly in the first timeslot of each second to maintain timing.
With its time slot definition and variable epoch size, the TD220MAX provides a generic TDMA
implementation that can be used by an external Communication Manager (CM) to support a variety of
TDMA schemes. A CM is responsible for making decisions regarding timeslot, frequency, power, and
payload organization. The TD220MAX is responsible for requesting data from a CM for upcoming
timeslots, forwarding messages received wirelessly to a CM, and wirelessly transmitting messages
received from a CM using the specified timeslot, frequency, and power. All communication between the
TD220MAX and a CM is done using STFP.
2.1
Front Panel Connectors and Indicators
Figure 3 shows the transceiver's front panel connectors and indicators. These items are referenced in the
installation steps and in various other locations in the manual. The transceiver's LED functions are
described in Table 6 on Page 12.
LED
INDICATORS
SERIAL
CONNECTOR
(DB-25)
MDS 05-6906A01, Rev. R
USB
CONNECTOR
DC INPUT
POWER
Figure 3. Front Panel Connectors & Indicators
TD220MAX Technical Manual
ANTENNA
CONNECTOR
(N FEMALE)
3
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