Isolation

timbitson: WeatherStationGrounding.pdf / local copy

HA4B - RS232 Isolated 1-Wire Host Adapter

Optical Isolation

Gladstone Family surge protection

.1 A 250 V fuse
1N5906    (12 V Zener)  Zener (TVS): 1.5KE10ACCCT -- 10 Volt 1500 Watt Unidirectional TVS.
1N5817    (1N4004)      1N5404GICT -- 3Amp 400PIV diode

DataShield RS-232 Dataline Surge Suppressor

SUPPRESSION 1 set RJ45 in/out jacks, protects wires 1-8, 18V clamping.

Tripp Lite DataShield DB-9 Dataline Surge Suppressor

Offers protection on all 9 lines, plus D shell chassis. Peak pulse clamping voltage: 18V

Phone line surge protection is not suitable for data line protection. The clamping voltage is typically several 100s of volts. You can get dataline RJ45 connectors built into the power strip which have 18 volt clamping which may be more suitable.