Föderl-System Signal Transmitter Telephone

The Föderl-System Signal Transmitter Telephone was an early 20th-century telecommunications device designed for industrial or specialized signaling use. Unlike standard telephones of that era, which were primarily for voice, a "Signal Transmitter" telephone was often built to send specific electrical pulses or coded signals across a network—similar to how a fire alarm or a railway signaling system operates—while still maintaining basic voice capability. They represent a bridge between telegraphy (coded signals) and modern telephony (voice).