Ext Idi: Insert Data In; Ext Ref: External Reference, Top Bnc Port, J10; Rs530/422/V.35 Interface (Standard); Interface (Optional) - Comtech EF Data DMD50 Installation And Operation Manual

DMD50 Universal Satellite Modem
3.7.2.5

EXT IDI: Insert Data In

External IDI is used only for E1/T1 Drop and Insert applications. The available T1/E1 Frame
Source selections are External, Internal, and IDI/DDO Loopback. The T1/E1 Frame Source
selections can be accessed in the INTERFACE/RX SETUP menus. If Ext IDI is selected as the
RX Buffer clock, then user must first specify T1/E1 Frame Source.

External (RX Buffer Clock recovered from the data)

Internal (RX Buffer Clock recoverd from the internal clock)

IDI/DDO Loopback (RX Buffer Clock recoverd from the data and looped back)

3.7.3 EXT REF: External Reference, Top BNC Port, J10

This is not actually a clock, but does have some clocking implications. When the external
reference is used, the master oscillator within the modem is locked to the external reference, and
the internal accuracy and stability of the unit assumes that of the External Reference. Therefore,
not only are the transmit frequencies locked to the external reference, but the modem's internal
SCT Oscillator is locked to the external reference as well.
3.8

RS530/422/V.35 Interface (Standard)

Data must be clocked into the modem by either the SCTE or SCT Source. If SCTE is selected as
the Tx Clock Source, then SCTE must be supplied to the modem on the EIA-530 port. The output
of the dejitter buffer will be clocked with this source. SCT should be used if SCTE has excessive
jitter.
3.8.1 G.703 Interface (Optional)
If the G.703 Interface is selected, then the Tx Clock Source will default to SCTE and the Clock
Polarity will default to Auto.
Loop timing with a G.703 Interface or Asymmetrical Data Rates requires external equipment at
the remote end that is capable of using the recovered RD Clock as source timing for (SCTE) SD.
The modem will not manipulate the clock frequency. Therefore, the transmit and receive clock
rates must be equal in order for the modem to perform loop timing.
MN-DMD50– Revision 3
External reference port input is specified at
.3Vpp to 5Vpp (Sine or Square wave)
Theory of Operation
3–14