Method and apparatus for polling subscriber terminals

Apparatus for polling subscriber terminals or the like in a two-way addressable communication network having a plurality of remotely located communication centers coupled to terminals to be polled comprising:

• means for generating a succession of polling command signals each addressed to a different one of a plurality of terminals to be polled;
• means for sending said polling command signals to the terminals to be polled via communication centers to which the terminals are coupled;
• means for successively receiving a response signal from each polled terminal via the communication center to which the terminal is coupled, the amount of time it takes the polling command and response signals to be communicated to and from each communication center, respectively, establishing a round trip signal propagation time for each communication center;
• and
• means for equalizing the round trip signal propagation times required to communicate the polling command and response signals to and from each of the communication centers;
• whereby the responses from the polled terminals are received in the same order in which the terminals are addressed by the polling command signals.

Apparatus, for polling subscriber terminals serviced by a plurality of remotely located two-way addressable cable television systems, comprising:

• means for generating a succession of polling command signals each addressed to a different one of a plurality of subscriber terminals to be polled;
• means for sending said polling command signals to a plurality of cable television headends, each headend coupled to relay polling command signals to different ones of said subscriber terminals;
• means for successively receiving a response signal from each polled subscriber terminal via its associated headend, the amount of time it takes the polling command and response signals to travel to and from each of the headends, respectively, establishing a round trip signal propagation time for each headend;
• and
• means for equalizing the round trip signal propagation times required to communicate the polling command and response signals to and from each of the headends;
• whereby the responses from the polled subscriber terminals are received in the same order in which the terminals are addressed by the polling command signals.