The E-Frog expands the functions of the Palmer PGA-01 TRILINE and can only be used in conjunction with it. It can be used to switch between two amps routed to the same speaker cabinet. The E-Frog consists of 2 power relays and an 8 ohm dummy load. The relay routes the inputs from amplifier A/B either to the internal dummy load or to the speaker cabinet output. Since the amp linked to the dummy load doesn't receive input from the TRILINE, the E-Frog dummy load functions as a guard against internal feedback - consequently the impedance only plays a secondary role. Speaker cabinets with 4, 8, or 16 ohms may be used.

The important thing is to match the amp output impedance with the speaker cabinet.