Comtech EF Data SMS-458B - Manual (Page 65)

SMS-458B Modem Protection Switch Revision 2
Theory of Operation MN/SMS458B.IOM
4–5
Note: JP8 external battery jumper is not supported in the switch chassis, and therefore
must be set to the OFF position.
4.1.2.6 Error Response Switch
The Error Response function is an error message function that indicates that the
command sent cannot be carried out because local processing is utilizing the modem
control bus, local keyboard control, etc.
SP1 position 6 is the error response switch. The “ON” position enables the error response
function, and the “OFF” position disables the error response function.
4.1.2.7 External I/O Interrupt Arbitration
The switch does not use the external I/O interrupt arbitration function.
Note: JP12, JP13, and JP14 must be in the “LEFT” position to disable this function.
4.1.3 Modem Control Interface Specification
The modem control interface is an EIA-485 serial communication link, which allows the
switch to maintain control of backup modems and verify the configuration of the prime
and backup modems.
The EIA-485 interface permits up to 32 devices to operate on a common communication
link, however, only modems and channel units may be connected to this communication
link. External remote communication to the modems and switch is done through the
external remote interface.
The user cannot configure the parameters of the EIA-485 interface. The baud is fixed at
9600 and parity is even. All devices communicating with the switch must have their
remote control interface configured to those parameters. Each modem and channel unit
must have a unique address.
For details of remote interface specification and configuration for each device, refer to
the respective Installation and Operation Manual.
4.1.4 Relay-Remote Interface Specification