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System Overview
There are three different control signal program plugs. Each plug is associated with one or more
of the selectable interface types, as shown in Table 2-1. Figure 2-7, A-C, illustrates each program
plug, and shows how control signals are routed through the channel interface and across the TDM
link by each program plug.
Interface Types
An interface type supports the type of equipment connected to the data channel. The correct set
of control signals must be On before a CPU port, terminal, modem, or other device can commu-
nicate through the TDM channel. The control signals for a particular application are determined
by the requirements of the device connected to the channel. For example, most modems require
control signals Request to Send (RTS) and Data Terminal Ready (DTR) to be On before data
transmission may begin. The interface types, along with the program plugs discussed previously,
ensure that the required control signals are exchanged between the devices connected to the op-
posite end of a data channel. The operator of a MEGAMUX PLUS system may also force selected
control signals On or Off, to enable or disable data transmission through a TDM system.
TABLE 2-1. CONTROL SIGNAL PROGRAM PLUG/INTERFACE TYPE ASSOCIATIONS
Program
Interface Type
Plug Used
CTA - CPU to
MM01
Terminal
CTB1 - CPU to
MM01
Terminal DCE/
DSR On
CTC1 - CPU to
MM01
Terminal DSR
On
CPL1 - CPL to
MM01
Private Line
Modem
CTP2 - CPU to
MM02
Terminal-Polling
CPM2 - CPU to
MM02
Modem-Polling
CDM3 - CPU to
MM03
Dial-up Modem
DM3 - Dial-up
MM03
Modem to CPU
Node M
Node S
Channel
Channel
DTE/DCE
DTE/DCE
Orientatio
Orientatio
n
n
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DTE
DCE
DCE
DCE
DTE
DCE
DTE
DTE
DCE
Application
CPU port at Node M channel communicates with
terminal at Node S channel. Control signals gener-
ated by CPU port and terminal.
CPU port at Node M channel communicates with
terminal at Node S channel. RCV controls DCE and
DSR forced On by TDM.
CPU port at Node M channel communicates with
terminal at Node S channel. RCV control DSR
forced On by TDM
CPU port at Node M channel communicates with
modem at Node S channel. Control signals gener-
ated by CPU port and modem
CPU port at Node M channel polls terminal at Node
S channel to establish data transfers. Control sig-
nals generated by CPU port and terminal
CPU port at Node M channel polls modem in a
multi-point polling network, with master modem
connected to Node S channel. Control signals gen-
erated by CPU port and terminal.
CPU port at Node M channel communicates with
one end of switched network modem link (dial-up)
at Node S. Control signals generated by CPU port
and modem.
One end of switched network modem link at Node
M communicates with CPU port at Node S. Control
signals generated by CPU port and modem.
036R660-000, Issue 10
2-21
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