The T type attenuator is a very useful circuit block that has the capability to simultaneously match two transmission lines and attenuate the signals traveling on them. It is a symmetric circuit and when its impedances are chosen correctly the I/O can be exchanged without affecting the signals. Unequal impedances can also be used with appropriate modifications. These and other characteristics are explained in the “T pad” post on the Signal Processing Group Inc, website. Please visit for more info.