The Keysight / Agilent / HP 4935A is a Transmission Impairment Measuring Set (TIMS) which measures wideband data and voice impairments . The frequency range over which measurements are made is 20 Hz to 110 kHz, in steps of 1, 10, 100, 1000, or 10,000 Hz. There are four permanently stored, fixed frequencies -404, 1004, 2804. and 2713 Hz. Any other four frequencies may be temporarily assigned and stored by the user.

Option 003 has this unit come with a battery pack and p/ar measurement in place of noise to ground measurement

Hewlett-Packard 4935A/4936A Transmission Impairment Measuring Sets provide the basic analog tests to isolate faults and to qualify circuits for voice, data or broadcast transmission at frequencies up to 110 kHz. The 4935A is compatible with Bell standards and the 4936A is CCITT compatible. Both of these test sets provide measurements of level versus frequency, noise with various selectable filters, Signal-to-Noise Ratio, Noise with Tone, Three-level Impulse Nose and 4-wire single frequency return loss. The 4935A performs the required tests to qualify the local loop for Digital Dataphone Service up to 56 kbps. The Peak-to-Average-Ratio (P/AR) measurement option on the 4935A gives system users a powerful yet simple measure of the combined factors which effect the overall data transmission quality.

Telephone companies, PABX and other telecommunications equipment service people will find the 4935A/4936A has the analog testing capability they need. Both instruments include standard dial and hold capabilities, independent transmit and receive impedances, level zero function, SF skip and complete unit annunciation.