You can build this device for programming most universal pager instead of spending hundreds of dollars on Motorola's. If you don't feel like hacking up a serial card, you can use an external level converter instead.
POOR MAN'S MOTOROLA PAGER PROGRAMMER INTERFACE
Short Version
January, 1997 Ron Whitney
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Most programmable Motorola pagers are programmed with special software
through three (sometimes four) contacts on the side/bottom of the pager.
These contacts are Send Data, Receive Data and Ground. The logic levels
are TTL compatible. (Mine measure 0-3V instead of the usual 0-5V)
The communication parameters are 9600 baud, 8 databits, 1 stopbit, no parity.
Normally, the Univeral Programming Adapter (from Motorola) plugs into a
computer's serial port and converts the RS-232C logics levels back to TTL.
An older serial card may be modified to interface directly with the pager.
1) Find a serial card with socketed 1488/1489 driver/receiver pairs.
2) Remove the 1488 and 1489 but leave the UART in place.
3) Create two headers to plug into each of the vacated sockets with the
input pin(s) bypassed (shorted/jumpered) to the output pin.
Note: On the 1488, three of the four devices have two inputs.
1488 1489
------ ------
2-3 1-3
4-5-6 (2 inputs, 1 output) 4-6
9-10-8 " " " " 10-8
12-13-11 " " " " 13-11
4) Plug the headers into the vacated sockets.
The logic levels of the TxD, RxD (and other) lines are now TTL level.
5) Create a cable to connect the modified port to the pager.
DB-25 DB-9 Function
2 3 TxD Transmit data TO the pager
3 2 RxD Receive data FROM the pager
7 5 SG Signal Ground. Common to pager
6) The port may be restored later by simply removing the jumpered headers
and reinserting the 1488/1489 chips.