What is the oldest signaling format described as 4 x 2 relay information?

• A. 9 pulses or clicks
• B. 4 x 2
• C. 10 PPS
• D. 40 PPS

Answer: (B)

The signaling format described as four by two relay information is the oldest because it uses a simple, mechanical relay arrangement to encode status events. In early alarm systems, four relays organized in two banks could be set to indicate different conditions without relying on timing or digital signaling. This basic, relay-based approach came before later methods that used pulse counts, timed pulses, or higher-rate signaling. The other options describe time-based or rate-based signaling (pulses per second or clicks), which are more modern developments. So the four by two relay format is the earliest described signaling method.