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3.6 SOURCES OF CONTROL
The unit can be controlled via COMPEL™, terminal, modem, or Display / push buttons. Each
of these methods of control is explained in the following sections, but you should see the
COMPEL manual for a complete explanation of the COMPEL system.
3.6.1 Local Control Enabled/Disabled
In some instances Local Control of a unit may be restricted by Network Control at the Uplink.
Disabling the local control function allows the user to view status and settings but does not allow
for changes to most of those settings. For a concise view of which controls are enabled and
which are disabled, see Table 20 (Page 39). When Local Control is disabled, the terminal
commands designated “Control Commands” are disabled, as are the front panel menus which
have the same effects as those terminal commands. To see which terminal commands are
disabled see Section A.2 (Page 44).
3.6.2 COMPEL™
The COMPEL command stream from the uplink is usually the unit’s primary source of control.
This asynchronous stream is multiplexed into the aggregate MPEG data stream at the uplink.
3.6.3 Terminal
You may access the terminal command interface by setting Serial Port 1 or Serial Port 2
“device” to “Terminal” (using front panel control, if enabled by Network Control). Terminal
default settings are 19200, N, 8, 1. With a terminal installed, you may access the terminal
commands, which appear on a help screen and are documented in APPENDIX A of this manual.
With the exception of the “R” and “H” commands, they are only available if local control is
enabled.
3.6.4 Modem
The modem command interface is similar to the terminal interface. That is, it does not use
special handshaking or special control characters for this interface, and only supports auto-
answer modems. In fact, the unit does not distinguish between an attached terminal and a
modem. To access the modem command interface, the serial port 2 “device” must be set to
“Modem” (using front panel control). To access user commands, the user must enter the correct
password at the prompt. The user then retains access until the “OH” command is received, or
two 10-minute periods pass with no user input. As is the case for the terminal, the user
commands are restricted when local control is disabled.
3.6.5 PAL / NTSC Selection
The UNITY4422 accepts both PAL and NTSC video. Whether the input is PAL or NTSC is
auto-detected, and the appropriate parameters are set under software control.