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DESCRIPTION
The LTC 8780 Series are data converter units that are
designed to operate with the Allegiant
matrix switcher/controllers and the LTC 5135 Series
Controller/Followers. The LTC 8780 Series converts the
biphase control code generated by the Allegiant system and
the LTC 5135 Series into standard RS-232, and converts
RS-232 back to biphase code. This provides the capability of
transmitting the biphase control code over conventional
RS-232 transmission media (phone modems, fiber optics,
microwaves, etc.). The LTC 8780 Series can also be used to
perform the Satellite Selector functions in Allegiant Satellite
system configurations in addition to operating as a 15
channel remote signal distribution unit. A conceptional
operational block diagram is shown in Figure 1 and may be
used for reference purposes.
The biphase control code generated by an Allegiant series
switcher can contain three types of data — receiver/driver
commands, Console Command Language (CCL) commands
that control the SatelliteSwitching
switcher/follower data. When used in the biphase to RS-232
conversion mode, the LTC 8780 can be configured to
selectively filter out each of these data types. This feature
can reduce the amount of data that must be transmitted
over the RS-232 interface. Utilization of this capability may
be required in cases where a low baud rate is being used to
transmit the control code of a large switcher configuration
having multiple keyboards that are operating simultaneously.
As a subpart of its selective filtering capability, the LTC 8780
contains an address-matching feature that can provide one of
two functions — it can disable transmission of CCL
commands that do not match the selected address, or it can
disable transmission of receiver/driver commands outside of
a 64-camera block defined by the selected address. In a
Satellite Selector Unit configuration, the LTC 8780 would be
configured using the address matching feature so that only
CCL commands associated with that specific Satellite address
CCL Commands
Select (S102-3)
Biphase
Biphase
Decoder
Receiver/Driver Data
Code In
Select (S102-1)
XPoint Data Select (S102-2)
Figure 1: LTC 8780 Series Conceptional Operational Block Diagram
®
series of video
®
functions, and
Address Select
DIP Switches
(S103 and S104)
Match
Match
Select
On
(S102-4)
Match
Off
Match
CCL Data
Address
Function
Select
(S101-4)
Match Receiver/
Driver Data
are converted. In its receiver/driver address matching
configuration, it can be used to limit the amount of data (as
would be generated in a large switching system) from being
transmitted over a RS-232 link operating at a low baud rate.
The LTC 8780 can be configured to operate as a signal
distribution unit with 15 separate biphase code outputs.
Either "star" or "daisy chain" wiring configurations may be
used when connecting to the biphase outputs. Each output is
capable of driving up to 8 receiver/drivers in a "daisy chain"
configuration up to 1500 meters (5000 ft) using 1 mm
(Belden 8760 or equivalent 18 AWG) shielded twisted pair.
In this signal distribution mode of operation, the biphase
input code can be selectively filtered for the desired types of
data as described above for the RS-232 to biphase
operational mode.
The LTC 8780 Series provide a single RS-232 interface using
two RS-232 interface connectors. In most applications like
those described below, only one of the two connectors is
used. In a Satellite Selector configuration, the "CONSOLE"
interface of the LTC 8780 is connected to an Allegiant
CONSOLE port using the supplied cable. The interface
connector labeled "RS-232" provides a standard RS-232
interface for connection to a modem or other RS-232
compatible device. The data rate of the RS-232 interface is
user selectable for 1200, 2400, 9600 or 38400 baud. Note:
If the LTC 8780 is being used with variable speed
receiver/driver control codes generated by an Allegiant
series matrix switcher, a baud rate of 2400 or higher must
be used. When the RS-232 interface involves modems, the
LTC 8780 Series can be configured to send standard "AT"
type commands to aid in establishing the communication link
between the modems.
LED indicators are provided on the front panel to show
RS-232 data being received, RS-232 data being transmitted,
biphase data being received, biphase data being transmitted,
and power ON. See Figure 11.
Combiner
Biphase
RS-232
Data
Biphase
Output
Data
Source
(S101-3)
6
RS-232 Baud
(S101-1, 2)
And Control
Select (S105)
Console
Connector
Console Output
CTS
RS-232
Converter
RS-232 Output
RS-232 Input
RTS
CTS
DTR
RS-232
Data
Connector
Biphase Code
Biphase
Distribution
Code Out
Unit
Biphase
Output
Connectors
S933A05AE
2
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