I don't have an autosampler. Can I use the sequence table to start acquisition in such case?

Yes, you can. There are two possible intentions of using the sequence table for starting the acquisition:

1. Using sequence for manual injections
   You could define parameters for a series of injections in advance in a sequence table and then inject them one by one manually. In such case, the start must be external (individual runs in sequence cannot be started from Clarity). 
2. Using sequence for automatic injections without an autosampler
   In such case, the sequence must be in the active mode (set through Sequence Options dialog). Sequence sends a command to the sampler (over a serial line or by digital output) and waits for the start signal from the detector (again over the communication line or digital input). Without an autosampler, it is possible to start the acquisition by using the digital input and output specified in Ext. Start Dig. Input and Ready Dig. Output section of the System Configuration dialog.

How to set digital input and output to start the sequence without an autosampler?

• In case the injection is performed by some controlled valve or instrument (typically EAS analyzers) not supporting the Injection marker by digital output, the common solution when using the DataApex's A/D board is to interconnect the digital output set for Ready Out signal directly to the digital input set for Start In command. The digital input on the instrument starting the next run will be connected in parallel. With a controlled valve, the injection is then performed during the actual run by switching the valve (or valves) from the Clarity Event Table.

Events must be set in the Event Table accessible from the Method Setup dialog.

• In case no A/D board is used and the devices are not offering those digital inputs and outputs (for example with Agilent GC 5890), the suggested workaround will be to use the DataApex Virtual Digital Input Output Loop (auxiliary device, requires A24 LC or A23 GC Control license) to simulate the input/output needed - (those are virtually interconnected).

For more detailed info refer also to Clarity Getting Started manual, chap. 6.