The LX1FF660 is a replacement coil for the TeSys F contactor range, wound for 660...690 V AC 50 Hz control circuits. It's the part you pull when the original coil opens or shorts — not a contactor itself, just the electromagnet that pulls the main poles in. Coil technology is AC 50 Hz with no built-in suppressor module, so you'll need to add an RC snubber or varistor across the terminals if the PLC output driving it is solid-state. Closing time runs 23...35 ms, opening 5...15 ms — fast enough for motor starting, not for precision synchronizing. Mechanical durability is rated 10 Mcycles, and the maximum operating rate at 131 °F (55 °C) is 2400 cycles per hour.
Sourcing reality — obsolete
If you're holding a BOM that calls out LX1FF660, verify the control voltage on the existing contactor base and cross to the current TeSys F coil offering at the same 660-690 VAC 50 Hz rating.
The 660...690 V AC 50 Hz control voltage is unusual — most industrial control in North America runs 120 V or 240 V, and even 480 V is rare for a coil. This coil is built for 600 V class systems (common in Canadian and some European 690 V distribution) where the control transformer taps off the line side. Drop-out voltage is 0.35...0.55 Uc (about 231...380 V), so it won't drop out on a sag to 50% — that's intentional for ride-through on weak grids. Inrush power is 550 VA at 50 Hz, hold-in drops to 45 VA. Heat dissipation runs 12...16 W at 50 Hz. Coil resistance is 254 Ohm at 68 °F (20 °C), inductance of the closed circuit is 28.9 H. That inductance, combined with the lack of a built-in suppressor, means the flyback voltage on de-energization can hit several kV — plan for external suppression if the driving contact is electronic.