The HC5503T is a low cost Subscriber Line Interface Circuit (SLIC) from Intersil that replaces the components of a discrete Transformer Analog circuit design. The monolithic integrated design provides improved performance and system reliability. The HC5503T provides: Current limited DC feed to the subscriber loop, maintains a flat frequency response over the voice band and beyond, has self resetting thermal protection that allows conversation to continue while the fault is present, provides a TTL subscriber off hook indication even in the presence of longitudinal currents, and limits system power consumption on short loops. The HC5503T provides balanced 2-wire transmission and has excellent longitudinal balance, while providing on hook transmission and longitudinal current rejection in both the on-hook or off-hook conditions. The SLIC needs only one +5V supply in addition to the main battery supply for loop current and operates over a range of battery voltages (-24V to -58V). Available in 24SO packaging. The HC5503T is ideally suited as a replacement for discrete line circuits in low cost analog PABXs, small Office/Home Office products or Small Key Systems.