Additional electro-mechanical signaling device for Telefonbetrieb.Durch the electromechanical system very loud Signalisierung.FUNKTIONElektromechanischer AussenweckerWK 971 - two-tone sound-polarity protection (Attention, please only use terminals 1 and 2) - separate connection compartment for exterior and interior plastic body, GM reinforced - Surface Mounting 230V power connection with SAR power relay performance characteristics Operating voltage WK971, 230 special model AC 230 V / 50 Hz, impedance> 8 ohms at 25 Hz, the operating voltage level (Measured in small reverberation chamber) WK 971 > 105 dB (A) Protection IP 43 WK 971