08-01-2010, 10:20 AM
Unfortunately, there does appear to be an error in the circuit depicted on p176 which might explain your difficulties in understanding it. I believe both contacts (PIC SR and LOWER NPR) should be back contacts. See typical circuit X71500.
When the picture is turned on PIC SR drops, providing a feed to the Agastat. The time delay is selected by the value of the resistor, and 470k is usually used in this application which results in approx. 47 seconds. Once the Agastat has timed, the PIC JR will energise, and if nothing else has changed - i.e. barriers still up, PIC SR is re-energised, the picture is blanked and the PIC JR circuit is reset - hence the slow-release feature.
Note that there is no inductor - the book has a slightly ambiguous symbol for a resistor.
When the picture is turned on PIC SR drops, providing a feed to the Agastat. The time delay is selected by the value of the resistor, and 470k is usually used in this application which results in approx. 47 seconds. Once the Agastat has timed, the PIC JR will energise, and if nothing else has changed - i.e. barriers still up, PIC SR is re-energised, the picture is blanked and the PIC JR circuit is reset - hence the slow-release feature.
Note that there is no inductor - the book has a slightly ambiguous symbol for a resistor.