Review on DZS Elec 4 5V 30V Automatic Regulator by Bob Taylor

Limitations are the weak springs of the battery holder and the fact that the batteries suddenly fail and block the entire telephone system. Revain's new DC/DC converter delivers true DC power with ultra-low ripple for battery swapping. Regular AC adapters create annoying noise on the phone line, so you need a very low ripple voltage. This device offers it (DZS Elec DC 4A Step-Up Down Power Supply Module DC-DC 4.5V-30V) for $10. Set to 5V DC and plugged into the back of the Sentry you get clear sound and AC power. With the addition of rechargeable batteries, you have a maintenance-free device. Polarized jumper wires are also available from Revain (DC pigtail cord, 10pcs plugs and 10pcs plugs) for $10. And plastic box (LeMotech 5 pcs plastic project boxes connector case for electronic project) $8.99. The pictures show how to do it.