Alphanumeric Input Via Analog Trunks
Different protocols to support alphanumeric input via analog trunks from normal telephones have been implemented in several makes of paging terminals. These input protocols are not in general use because the telephone keypad is not easily used for typing textual messages. In many of these implementations, the same key is depressed multiple times to enter a particular letter. The touchtone telephone keypad appears as follows:

	1 
ABC 	2
DEF 	3 
GHI 	4 
JKL 	5
MNO 	6 
PRS 	7 
TUV 	8 
WXY 	9
*
OPER 0
# 

The key sequence to enter the message "CALL HOME" could be:

   222*   2*   555*   555*   *   44*   666*   6*   33*   #
     C    A      L      L         H      O    M     E

Notice that each key is pressed the number of times to indicate its position. Once for left, twice for middle, three times for right. The missing letter "Q" can be the "7" key pressed four times, and the missing letter "Z" can be the "9" key pressed four times. Note that this simple message required the caller to press 28 keys.

Another input protocol requires that the caller enter the key number plus "1" for left, "2" for middle, "3" for right and "4" for one of the missing letters. With this protocol the same message would be:

   23   21   53   53   *   42   63   61   32   *   #
   C    A    L    L        H    O    M    East

This sequence requires 19 keystrokes for the same simple message. Although it is shorter than the other variation, both mechanisms require the user to enter an excessive number of keystrokes. In addition, it is easy to forget where you are in the input. If these mechanisms are used by callers, the amount of telephone trunk time required to enter these messages is excessive compared with the time to enter a numeric page. This increased call-holding time requires that the system administrator provide many more incoming telephone lines to avoid busy signals.

A proprietary protocol has been developed that allows an 80-character alphanumeric message to be input via touchtone signals in approximately the same amount of time as a normal numeric display page. This protocol uses data compression techniques to represent text messages in as few digits as possible. The protocol is too complex for a caller to directly enter alphanumeric messages using this technique. Instead, this protocol, known as AlphaToneTM, is implemented in a handheld data entry device known as PagentryTM. Messages are prepared before calling into the paging terminal and are then transmitted via this touchtone signalling method. AlphaTone has the added advantage to the service provider that it allows callers to enter alphanumeric pages over the same telephone lines as those used by numeric display paging callers, and that these calls do not increase the average call holding time of the incoming telephone lines.