Sound module for several access doors systems. 4+n installation.
On EL551 sound module for systems with several door panels external switching units are not required.
Two selectrable electronic call types, allowing the tenant to distinguish which door is calling.
When channel is busy, the light push button changes colour and accoustic tones are reproduced on the door panel if someone tries to make a call.
On building with one access only use an EL555 sound module.