[VoIP] Asterisk and Payphones

[Steph Kerman]

Actually... it would not care.  All single coil coin relays short 
circuit their own winding upon operation, replacing the load towards the 
CO with that 1K resistor you see mounted on the contacts.  The shorted 
coil keeps the relay operated for ~450 mS regardless of the duration of 
the applied voltage.  The trigger contacts open during armature 
operation, disconnecting the coil and/or resistor from the line when the 
armature restores at the end of 450 mS.  

This however is NOT true for double coil coin relays used in earlier 
3-slot sets.  They remain operated for the duration of the applied 
voltage and open the trigger contact when voltage is removed.

Steph

Mark Rudholm wrote:
> Well, the reason for doing the timing in hardware is that I don't 
> trust the PC or the software to not set the strobe line high and
> leave it there, which would leave my coin-relay energized all day, 
> possibly damaging it (I don't have the relevant BSP, but I doubt the 
> coin-relay would be happy with a 100% duty-cycle).