The exchange shall handle traffic to and from, as follows:
5.25.1 Subscribers connected within their own exchange (including all subscribers of host and remote exchanges).
5.25.2 Other local exchanges (originating, terminating, and transit).
5.25.3 Tandem, toll, and international exchanges.
5.25.5 Announcement machines (connected to exchange).
5.25.6 Operator services (including trunk offering by operators).
5.25.7 Test equipment in the exchange.
5.25.8 Coin Box services (for special cases like in new developing areas, during construction, etc., where the services might be required).
5.26 Traffic Loads
All digital exchanges shall be designed to handle average subscriber traffic loads (bothways) of 0.8 erlang per trunk during the busy hour.
It is recommended that all digital exchanges should be designed to handle an average of 0.1 erlang per line for low traffic exchanges, and 0.18 erlang per line for high traffic exchanges.
5.27 Average Dialing Time
The following reference information is provided for the design of the switching system:
5.27.1 Pre-dial interval: 2.0 seconds (time after receiving a dial tone before the subscriber starts dialing).
5.27.2 For DTMF (Dual Tone Multi Frequency): 0.6 seconds for each digit.
5.27.3 For rotary dialing: 1.5 seconds for each digit.
5.27.4 MF (Multi Frequency) sender signaling: 10 digits per second.