There are two types of pulse amplitude modulation:

The 4D means four data symbols (two bits), the PAM5 is Pulse Amplitude Modulation with five signal levels.

However, they have the considerable advantage that they may be easily transmitted as two pulse amplitude modulation (PAM) signals on quadrature carriers, and can be easily demodulated.

The most novel part of the conception of the exchange design was the use of pulse amplitude modulation and time division multiplex techniques for the transmission of up to 100 conversations over a common channel, which was well ahead of its time.

In 1964, he became Head of the Advanced Development Group at Standard Telephones and Cables Ltd., where he continued the development of fully electronic telephone switching equipment including a pulse amplitude modulation exchange, retiring in 1969.

TC-PAM (an acronym for Trellis Coded Pulse Amplitude Modulation) is the modulation format that is used in both HDSL2 and SHDSL, and provides vigorous presentation over an assortment of loop circumstances.