What does the GM spark control do?

[mdcptman]

Ok, i found this on ebay

http://www.ebay.com/itm/90-gmc-chevy-sbc-electronic-spark-control-tbi-350-/270968224414?pt=Motors_Car_Truck_Parts_Accessories&hash=item3f16f6fa9e&vxp=mtr

This is kinda a stupid question, but what does it do? Is it in addition to, or replace the module in the GM distributor? I am wondering, because if it controls the spark separate from the ECU, can it be added to control spark on a fuel only TBI conversion. OR, Say I convert to TBI, and opt to use the Duraspark distributor with vaccum and mechanical advance disabled, can this module be connected to the ECU instead of connecting the GM module outside of the distributor as I have seen others do.
I hope this question makes sense. thanks in advance for the input!

[Bill USN-1]

It would be best if you go to this link and look at the description of the different parts.
That is the

2. Knock control- ESC-electronic spark control. this sends the signal from the Knock sensor to the ECM to reduce the timing if it hears a ping.

It is part of the factory GM system but is not required when doing a conversion.

For timing control you need a distr with a magnetic pick up to trigger the

10. Distributor/EST-electronic spark timing- Also know as the ICM-Ignition control module. For FI you will need to decide if you want a complete conversion (fuel and timing) or partial (fuel only).
For fuel and timing you will need a distr with a magnetic pick up. You have 2 choices.
a. The duraspark conversion. DS Distr conversion has the EST mounted external on a sheet metal heat sink.
B. The small cap EFI distr. Small Cap EST is mounted internal. This distr is made by grafting a GM upper onto an IH lower distr by a machine shop.
For the fuel only conversion you will retain your stock distributor but will need a special filter to run between your ignition and the computer.
EST

Which then sends the distr pulse to the ECM and then receives the timing signal back from the ECM and fires the coil and the correct time.

[babywag]

That is for retarding timing in combination with the knock sensor.

It connects between the knock sensor/ecm.
When a knock is detected the signal is relayed to the ecm, and the spark is retarded if needed and if enabled.

The ECM controls timing.

It is not to replace the ignition module, it is in addition to it.
Yes, it could be added to a fuel only system with the correct wiring.
Or, it could be left out if you don't want to run a knock sensor.

[mdcptman]

Thanks Guys, I understand now

[mdill]

The box you referance is the knock sensor signal detector/filter.
The knock sensor was shared between lots on models, the filter/detector came in
lots of flavors depending on engine noise cheriteristics. (it figures out if the noise is just engine noise vs. a knock, and then grounds the signal back to the ECU if it thinks it is a knock)