Additional electro-mechanical signaling device for Telefonbetrieb.Durch the electromechanical system very loud Signalisierung.WK 978 is the name of the similar unit of the German Telekom.FUNKTIONElektromechanischer AussenweckerWK 971 - two-tone sound-polarity protection (Attention, please only use terminals 1 and 2) - separate connection compartment for Outdoor and indoor plastic body, GM-reinforced surface mounting performance characteristics NR.Bestell Order no. BZT Nr.WK 971 Pebble gray RAL 7032 103 641 CAn 1-509.15.1.07 A small phone systems that do not provide enough energy is available, it may be necessary that the following Articles shall be inserted: WK 971 (230V) with Starkstomanschaltrelais 1 - 509.15.1.11Betriebsspannung WK971 (Standard) 45-50 V AC / 23-54 Hz, impedance> 8 ohms at 25 Hz, the operating voltage level (measured in small reverberation chamber) WK 971> 105 dB (A) Protection WK 971 IP 43TECHNISCHE DATA