Need a timed circuit of some sort.

 I have an omega gps2000 connected to my matrix 2.5 alarm. the siren output is connected the alarm sensing input on the gps2000. This way the unit calls me when the alarm is tripped. However I've noticed that it takes for the siren to stop before the unit calls my cell phone.

  I believe the gps2000 has some sort of timer and looks for a + then nothing on the alarm input to tell if the siren is constantly blasting or is just chirping from arming/disarming.

  I would like to build a circuit that would basically cut the + to the alarm input on the gps2000 after say 10 seconds.  any ideas?

look at the constant to momentary output

http://https://www.the12volt.com/relays/page5.asp#ctm