External console control for terminals

To all Conserveraffectionados,

I am considering building an external piece of hardware that will permit the 
console manager to control whether a terminal close to the host, as well as 
the host, is also connected and able to display, and/or able to transmit 
keyboard information to the host.  This device would be a simple "Y" 
connection on the host's transmit data leads, allowing the local terminal 
and the remote conserver to see every character from the host.  However, 
transmit data from the local terminal, or from the conserver, could be 
remotely interrupted.

It may be necessary to use a device like this for several reasons:

Some hosts I deal with, like HP3000s, have a "block mode" which causes the 
terminals to "answer back" with cursor positions, etc.  If a remote terminal 
is connected, via conserver, and a local terminal near the host is also 
connected, and the host enquires information from the terminal, it will get 
2 responses if both are able to respond.

Sometimes it is necessary to grab the console from the local terminal so 
that the remote console operator is assured he or she is in complete control 
of the session during critical installations.  And the opposite may be 
necessary for the same reason.

I have made other devices on this scale and can do my own printed 
circuitboard design.

My question to the group is:  Does anyone know of a device that does this 
and which is already available?  I am exploring a software feature of the 
MRV In Reach terminal server that is supposed to have this functionality, 
but I have not yet tested it.  If something already exists out there, I 
would prefer to use it, rather than "re-invent the wheel."  I know that ASP 
makes a Cat Walk box that comes with each host licensed for their Vantage 
program, but I don't think they sell this separately.

Conserver is a great product.  The additional capability of this device 
would make it possible to add another class of machines to those that I can 
currently manage.

Thanks for any help you can lend me,

Greg Brown
Midrange Communications Specialist
CSC San Diego Data Center

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