Kevin… Passed Driver, made a reference to power supplies in

http://yourmodelrailway.net/view_topic.php?id=15131&forum_id=21&jump_to=283867#p283867

so I thought I would tell what my layout uses outside of the supply for the NCE DCC system

40v DC for Telephone Company relays
16v DC for Kadee electromagnets
12v DC for LEDs
19v DC for my One-wire CDU for turnout solenoids
16v AC for Tortoise using diodes as per Fig 3 on the attached

What is the 40v supply for?

Save those transformers found on household/office items. They will come in useful for DC circuits. Do not use for DCC operations unless you are absolutely sure the output is smooth.
Printers, routers, DVD drives, monitors, computers, electric razors. They come anywhere from 5v and a couple of hundred mA to 20v and 5A. My turntable  motor used a 12v 400mA transformer from an old electric razor driving a PWM board.

Nigel

Chris, the 40v is used for  relays that require such voltage - usually old telephone exchange relays as they have many contacts - the one I have, have  6 change over contacts.
Relays are used in my signalling system.

Cor, I haven't worked on a relay like that in many years …
When I started work on my Tiree layout,  I found a dozen PSUs inside the two control panels , when ever the original builder added something he just added a new PSUs.

After much studying,  I replaced the 12 with 3. 
+- 12 v and +5v

Also everything  had been built with both +- wiring. By tying the 3 PSUs together properly , and using a bus bar,  I removed miles of wire.