VoIP communication (voice over internet protocol communication) may be restricted by your provider. Some service providers may restrict VoIP communication (voice over internet protocol communication). It is recommended that you check with your service provider before using this product. This product is not for commercial use. Please use AGEphone Business or AGEphone Cloud for commercial use. The on-hold function of this product does not work if RFC2327 or RFC3264 is not supported. DTMF is also supported, but may not work properly if the DTMF type is different. Please be careful not to forget to disconnect after you finish using Hikari Denwa from your smartphone. A third party may be able to intercept radio waves that reach over walls and other obstacles. Please make security settings at your own risk and discretion. Please note that we are not responsible for any malfunctions or problems caused by downloading, setting, or operating the application software for using Hikari Denwa with your smartphone. The transfer function is a paid function. The call forwarding function is a paid function. Please make sure that your IP phone service (server) supports the REFER method before purchasing the paid feature. If it does not meet this requirement, it will not work. Ad-free function is a paid feature. The volume of incoming calls may be low. When answering an incoming call, the phone may be silent for a few seconds. When answering an incoming call to the standard phone application during a call, the speaker may switch to the external speaker, but this can be resolved by switching the external speaker on or off. Noise may be heard when answering an incoming call. For other limitations of AGEphone series products, please also refer to this page.