Agilent Technologies 5975C TAD VL MSD Troubleshooting And Maintenance Manual page 229

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Electronics
signal. On receipt of the ready signal, the desorbtion cycle begins. When a
specific temperature is reached, the purge-and-trap closes a contact to
indicate the run has started.
The ready pin on the remote start connector on the GC is held low at all times
except when the GC, MSD, and data system are all ready. On system ready, a
logic high of 5 VDC is present between that pin and any ground. This same
high can be detected between the ready and ground pins on the remote start
connector on the MSD.
Start run input
The best way to generate a start run signal is to use the remote start connector
on the GC. Since remote start cables are made for most common devices, this
is often the simplest way. A general-purpose remote start cable (05890-61080),
is also available which terminates in spade lugs. Care must be taken to ensure
that the system is actually ready before the start run signal is sent.
If necessary, the remote start connector on the back of the MSD can be used to
send the start run signal. A contact closure between the start and ground pins
will start the run if the system is ready.
5975 Series MSD Troubleshooting and Maintenance Manual 229