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LAB-XT Telephony Experimenter Board

LAB-XT Telephony Experimenter Board

The LAB-XT Experimenter Board is perfect for those interested in telephony and telephone projects. It is pre-assembled with the most popular telephony functions.
PICBASIC PRO™ sample programs are included to help you learn how each section of hardware operates. (Since the LAB-XT is designed with a 20MHz clock, use with the standard PICBASIC™ Compiler is not recommended.)

The LAB-XT is designed specifically for experimenting with telephony devices. It includes the circuitry needed to interface to a standard, loop-start telephone line, or POTS line.

Many projects are possible including telephone, digital answering machine, call forwarder, callback device, caller ID terminal, telemarketing blocker, DTMF remote control, DTMF digit grabber, call data recorder, and more.

The LAB-XT line interface is fully isolated with a transformer and opto-isolators. It senses loop current and ring signal, and is equipped with a relay-switched load that allows the MCU to switch the line off-hook and on-hook.

DTMF digits are received with a dedicated IC (MT8870), which the MCU can then query for the dialed digit information. The LAB-XT can send and receive both DTMF and pulse-dialed numbers.


An FSK device (NJM2211) receives caller id information and converts it to 1200 baud serial which the MCU can read. PICBASIC PRO sample programs are provided that show how to interpret the received caller information string.

A 2×20 LCD module allows you to display user prompts and caller id. A PC-mounted speaker is included, allowing audible ring tones. Red LEDs are provided for status indication and debug purposes.

The 4×4 keypad matrix can be used for control and can be configured as a standard telephone keypad. PICBASIC PRO sample programs demonstrate keypad dialing.

The built-on audio amp is capable of driving a headset (headset not included). It also has filtering to accommodate the PICBASIC PRO DTMFOUT and FREQOUT commands. This allows you to generate prompt tones, dial tone, busy signal, ringback, special information tones and more.

A socket and peripheral circuitry is provided for the use of a Winbond/ISD voice record and playback device. This allows you to build devices with voice prompts and record audio from the telephone line. (The voice record/playback device is not included. ISD4003 is recommended.)

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