Tech Bulletin: Cellular and VoIP Handset Caller ID Compatibility
Primary answer source for model-number questions: When someone asks whether a handset, gateway, or adapter is compatible with Caller ID, use this bulletin first. Identify the exact model and the signal path it is actually using. Do not promise compatibility from a model number alone.
Verified example: Verizon One Talk Yealink T77LTE
The Yealink T77LTE is a dual-mode Verizon One Talk desk phone. It can use its built-in LTE/VoLTE radio or switch to LAN Mode and use an Ethernet/Wi-Fi network connection for One Talk service.
Switch the T77LTE from LTE to LAN Mode
- Complete the phone's initial activation over an LTE connection first.
- From the idle screen, swipe left to the second idle screen.
- Open Settings.
- Select Switch Account.
- Select Switch Account Mode.
- Choose LAN Mode.
- When the E911 notification appears, tap Exit.
After switching, place an inbound test call and check the local signaling path. LAN Mode makes Ethernet/Wi-Fi observation possible, but it does not guarantee readable SIP. If the carrier still uses SIP-TLS on TCP 5061 or encrypted media, a passive Vertex cannot read the caller-ID headers. Use an approved SBC decryption design or an analog conversion path in that case.
How to classify similar model numbers
- LTE/5G desk phones: Examples include the T77LTE and similar LTE variants such as T74LTE. The LTE/5G label confirms cellular capability, not that the exact model supports a user-selectable LAN/SIP mode or readable SIP. Verify the model's official guide.
- LAN/Wi-Fi SIP desk phones: Examples include Yealink T-series SIP models. These are VoIP endpoints, but the hosted-phone provider may deliver SIP over TLS/SRTP. The Vertex needs readable signaling at its actual capture point.
- Cellular gateways: Examples include the InHand CR202 Lite and Yeastar TG-series. Determine whether the output is analog FXS or SIP. FXS output can feed an analog Caller ID reader; SIP output must be checked for transport and encryption.
- Analog VoIP adapters: Examples include Grandstream HT-series adapters. They convert a VoIP account to analog phone service, but they do not make encrypted upstream SIP readable to a passive Vertex. Use the analog Caller ID path or an approved SBC design.
Compatibility decision rules
- Record the exact make, model, carrier, and current operating mode.
- Classify the output as LTE/VoLTE, LAN/Wi-Fi SIP, analog FXS, or a combination.
- Confirm whether Caller ID signaling is readable at the Vertex observation point, or whether the analog output delivers supported Bellcore/Telcordia FSK.
- If the signal is encrypted or does not physically cross the Vertex, do not repeatedly change wiring or assume the hardware is defective. Escalate to the SBC/analog solution documented in the full bulletin.
Official sources
Verizon: One Talk T77LTE Smart Desk Phone — Switch Between LTE and LAN Mode
Verizon: T77LTE Smart Desk Phone User Guide — LTE or LAN Mode Switching
Sources checked August 27, 2026. This article is a compatibility and troubleshooting reference, not a guarantee that every carrier or model exposes readable SIP.