Stuck in circuit analysis
This is not the best drawn schematic.  Apparently there is a single relay, which is shown in several parts in the schematic.  That by itself is fine.  The problem is that the coil is designated RL1, but the various switch parts just RL.  Despite the different designators, it seems that RL1 and RL are really the same relay.

At least the NO and NC options for each switch part are clearly labeled.  NO stands for "normally open", and NC for "normally closed".  The NO options are therefore open when the coil is not driven and closed when driven.  The NC options are closed when the coil is not driven and open when driven.

A NAND with both inputs tied together is just a inverter.  When the opto is activated, its output is pulled low.  The NAND gate inverts this so that its output goes high, which turns on T3 and activates the relay.

The circuit for driving the opto is suspicious at best.  Note that the diode is in series with the capacitor.  That means the capacitor will eventually charge up and no current will flow thru it in steady state.  Perhaps the relay is only intended to turn on for a short time after powerup.  However, since there is no definite way to disharge the cap, the amount of time for this to reset so that the relay will again come on at next powerup is undetermined.  For a perfect cap and diode, the capacitor would charge up once and then stay charged forever, regardless of power being turned on and off.