| PoE IP system | 1920 × 1080 pixels; commonly supports H.264 or H.265 video compression. | One Ethernet cable for data and power; Cat5e or better is normally used. | Look for an outdoor rating of at least IP54; IP65 offers stronger protection against dust and water jets. Metal or UV-resistant housing is preferred. | Confirm PoE standard, network bandwidth, SIP or ONVIF support, monitor compatibility, and availability of a local network connection. | Approximately US$150–450 for a basic equipment set, excluding installation. | Strong option when firmware updates, configuration backups, open protocols, and replacement indoor stations are documented. |
| Two-wire digital system | 1920 × 1080 pixels is available on newer systems; image quality depends on the bus converter and cable condition. | Two conductors may carry power, audio, video, and control signals. | Suitable for sheltered or exposed entrances when the outdoor station has a sealed enclosure, drainage design, and corrosion-resistant mounting hardware. | Verify bus protocol, maximum cable length, conductor size, voltage drop, distributor capacity, and compatibility with existing monitors. | Approximately US$120–350 for a basic single-door equipment set, excluding installation. | Good for replacing older systems if the supplier provides migration accessories, wiring diagrams, spare parts, and a published product life cycle. |
| Four-wire analog system | 1080p video requires compatible digital conversion; many older four-wire systems do not natively provide Full HD. | Separate conductors are typically used for power, ground, audio, and video. | Cable quality and distance have a significant effect on noise and image stability; weather sealing should be checked carefully. | Confirm signal format, monitor pinout, power requirements, cable distance, door-release voltage, and whether a converter is required. | Approximately US$80–250 for a basic equipment set, excluding installation; conversion hardware may increase the total cost. | Cost-effective for simple retrofits, but long-term risk is higher when replacement monitors or compatible camera modules are difficult to source. |
| Wi-Fi video door phone | 1920 × 1080 pixels is common; actual clarity depends on lighting, lens quality, Wi-Fi signal, and compression. | Wi-Fi for data with wired low-voltage power; battery-powered versions may require regular charging. | Choose IP54 or higher for exposed locations, a wide operating-temperature range, and a tamper-resistant mounting plate. | Test 2.4 GHz coverage at the entrance, confirm app and operating-system support, cloud requirements, local recording options, and door-lock relay ratings. | Approximately US$80–250 for the main device, excluding optional subscription fees and installation. | Convenient, but support depends heavily on app maintenance, cloud availability, privacy policies, and the supplier’s update commitment. |
| Multi-apartment IP system | 1080p video at the entrance is common; indoor stations may support different resolutions depending on the system design. | Managed Ethernet network, dedicated switches, controller hardware, and a central power supply are typically required. | Specify IP65 or better for the entrance panel, vandal-resistant materials, surge protection, backup power, and tested emergency release behavior. | Check apartment capacity, elevator integration, access-card support, SIP compatibility, VLAN requirements, cable distance, and emergency communication rules. | Approximately US$300–1,500 or more for equipment, depending on the number of units and access-control functions. | Prioritize documented firmware support, administrator training, replacement-part availability, remote diagnostics, and a clear warranty process. |
| Recommended minimum benchmark | Full HD 1920 × 1080; infrared or white-light assistance; usable image in both daylight and low light. | Use a wired connection where reliability and continuous availability are more important than quick installation. | Outdoor rating of IP54 or higher, operating temperature of approximately −20°C to 50°C, and corrosion-resistant fasteners. | Confirm voltage, wiring, network protocol, lock output, mobile-app support, storage method, and local legal requirements before purchase. | Compare total cost of ownership: device, power supply, cabling, installation, storage, subscriptions, maintenance, and replacement parts. | Prefer a written warranty, security-update policy, spare-parts availability, technical documentation, and support contact that will remain accessible after installation. |