Perdana FW, Ayuni SD, Wisaksono A, Syahrorini S. Prototype Social Distancing Reminder Using HC-SR04 Sensor At The Payment Counter Via A Smartphone: Prototype Pengingat Social Distancing Menggunakan Sensor HC-SR04 Pada Antrian Loket Pembayaran Via Smartphone. PELS [Internet]. 2021 Jul. 14 [cited 2025 Jun. 27];1(2). Available from: https://pels.umsida.ac.id/index.php/PELS/article/view/952