Possible Options for the first Resistor/Capacitor Circuit - RC1
turn on timed off - Set of timing units for RC 1 

R2
C1
Time
 20 M ohms
10 uF
120 seconds
 10 M ohms
10 uF
60 seconds
 4.7 M ohms
10 uF
30 seconds
 20 M ohms
1 uF
12 seconds
 10 M ohms
1 uF
6 seconds
 4.7 M ohms
1 uF
3 seconds
Remember that this is only a rough guide.  It is not a precise timer.
the schematic shows the related variations 
manually speed up the timed off
Use pin heads as a touch switch 
or 
Use a Push Button N.O. to instantly drain C1
Alarm stays active until you turn it off. 
A hidden touch point of two pinheads is all that you need.  Use a small capacitor at C1 (.1 uF) and it will appear to turn off instantly (about a half second). 
Or use a Push Button N.O. to instantly drain C1.
 Time on Delay
This circuit can be used to delay the activation of the circuit.  It can be used to give you time to set the circuit in a car alarm, for example, and have time to close the exit. 
The value of the Extra R must be at least a fifth the value of R2 to work because the Extra R and R2 become a voltage divider - the voltage must rise clearly above the half voltage mark.  To give more time, use a larger capacitor. 
No RC 1.
When the Inputs are Lo at pins 12 & 13, the circuit is active.  The circuit immediately turns off when the inputs go Hi.
turn off, timed on
 This is really a modification at the output. 
This was part of the exercise sheet in Exercise 2-2-5 Test Point 4. 
The RC timing table above is unchanged.  The output is reversed.