# Signaling System No. 5

> multi-frequency telephone signaling system

**Wikidata**: [Q7512768](https://www.wikidata.org/wiki/Q7512768)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Signaling_System_No._5)  
**Source**: https://4ort.xyz/entity/signaling-system-no-5