Скачать или смотреть Strowger: Testing 4 junction relay sets

These are 4 relay sets I built last year for the Dean Forest Railway, they interface between the strowger telephone exchange at Parkend and an electronic exchange.

I recently had them on the bench for modification, and thought I'd chain them together.

The phone is connected to the relayset on the left, which feeds it to the next, then the next, then the next... which is connected to a voip exchange in my home workshop.

When you pick up, Relay A operates, which in turn forwards the loop to the next stage (via R1 which is a 500R spool). It also operates Relay B, which has a heel end slug (a lump of copper which uses eddy currents to make the relay slow to release)

When you dial a number, Relay A reacts to the dial pulses, and forwards them to the next stage. Relay B is slow to release, so remains operated, and provides a hold signal on the P-wire back to the calling equipment.

The slow motion at the end was intended to show the relays cascading, but it happens too quick to see!