Is the battery included?

Yes, It is included, You can purchase replacement type A23 batteries here: https://www.amazon.com/dp/B01C57SPQ6

Can I add another reciever?

Yes, you can purchase an extra receiver here: https://www.amazon.com/STARPOINT-Operated-Receiver-Expandable-Multi-Unit/dp/B00XHWU7SI https://www.amazon.com/STARPOINT-Operated-Receiver-Expandable-Multi-Unit/dp/B075KYWD6Y

can the recievers be plugged in outside and operate safely? I wanted to get one of these so that way I can tell if someone is at the front door when

I would not believe that you could plug them in outside. The people at the company are very nice. I would send them a note and ask, but there is nothing in the information I have that would lead me to believe it would be safe to use outside.

Brand	SadoTech
Model Number	B00J4FHOB0
Product Dimensions	8.13 x 3.81 x 8.89 cm; 195.61 g
Color	wht
Name List for Name Plates	1 x Push Button + 2 x Receiver
Material	ABS
Wallpaper Pattern	Patented Design
Voltage	110 Volts
Quantity	3
Light Source Type	LED
Laser Class	SadoTech
Included Components	SadoTech
Are Batteries Included	No
Battery Type	Alkaline
Paint Features	SadoTech
Item Weight	195 g

SadoTech ワイヤレスドアベル 自宅、アパート、ビジネス、教室など用 - ドアベルリンガー1個&プラグインチャイムレシーバー2個、電池式、使いやすい、LEDフラッシュ付きワイヤレスドアベル、ホワイト

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Specifications

Common Questions

SadoTech ワイヤレスドアベル自宅、アパート、ビジネス、教室など用 - ドアベルリンガー1個&プラグインチャイムレシーバー2個、電池式、使いやすい、LEDフラッシュ付きワイヤレスドアベル、ホワイト