Speaker Volume Adjustable: Counter intercom speaker is loud and adjustable with clear sound. Can be easily mounted on the wall with tape, ideal for transmission distances up to 200 meters without interference. Perfect Combination: Indoor intercom is perfectly combined with the outdoor intercom, allowing you to talk to visitors outside your door. The doorbell sound effect is highly restored, allowing you to identify visitors outside the door according to the sound. 3W Power: Dual way counter intercom is designed with electro acoustic circuit devices, upgraded sound quality and high power output of 3w for both main and sub units, with clear and bright sound and high voice resolution. Fully Automatic Call Control: Window two way intercom system applies fully automatic call control, using duplex voice intercom talking technology, automatic recognition and processing of voice signals, the call process does not require any operation.