Before we talk about the DP-34A switch, we need to understand the design of DP-34 first. One DP-34 switch can connect up to 4 receivers, but at least 1 of the 4 receivers needs to be powered on at all times in order to provide power needed to run the switch properly. All the other DP-34 switches in this cascading system also need to follow this rule for proper functions. At least one receiver of the four connected to each DP-34 switch has to be powered on at all times; otherwise no power is passed through the switch, and the other switches that cascade afterwards would not work properly and the receivers cannot receive any programs.
The DP-34A multi-switch made and designed by Microyal has an extra input, which can hook up to a DC-24V power adaptor to provide power towards the switch. This way we do not require the receivers to be powered on at all times to provide power to the switches. When DP-34A is connected to the power adapter, the power supply that comes from the receiver (s) will be replaced by the power supply coming from the power adaptor. If DP-34A is not used along with an adapter, then the power will have to be supplied by the receivers. This design of internal power supply switch will only allow power to be passed from either the receiver or the adaptor to the switch.
It is quite obvious that the use of DP-34A will secure the whole cascading system and ensure it will function properly by having continuously supply of power at all times. The issue within the cascading system caused by DP-34 will be resolved by the use of DP-34A and we won't be having null function receivers due to un-powered switches. Therefore it is better to replace DP-34 switches with DP-34A switches to ensure a more stable and reliable satellite system.
to take a look at the specification of DP-34A and another cascading diagram.