Grandstream IP Audio conference Device. The GSC3510 is a robust SIP intercom speaker and microphone device offering voice functionality with both a high-fidelity 8W HD speaker and 3 directional microphones. The GSC3510 supports a wide-range of peripherals including Bluetooth devices, built-in whitelist and blacklists to easily block unwanted calls, intregrated dual-band WiFi and advanced acoustic echo cancellation.