PBX Music On Hold

I bought a cheap telephone PBX for my small business and much to my dismay it has horrible music that plays while the caller is put on hold. It's like midi Fur Elise or something. There seems to be no way to change it in the normal settings.

I popped off the top of it just to have a look inside and I noticed all the IC's are socket mount big old things and it's a pretty simple looking device. I'm just wondering if there might be something I can do to disconnect the music. Any ideas about what IC might be the culprit and what I might be able to do about it?

The IC's:

AT89S51 - 8-bit Microcontroller with 4K Bytes In-System Programmable Flash AT24CO4PC - 4Kbit, 2-Wire Bus Serial EEPROM DLT 8816 - This chip has a scratched top and looks like it is a re- badged processor, same form as the AT89S51 CS9370DGP - DTMF demodulator (there are 3 of these) HEF40106BP - Hex inverting Schmitt trigger PS2501-2 - High isolation voltage single transistor type multi photo coupler NEC 2501 - probably older version of the PS2501 HD74HC244P - Octal Buffers/Line Drivers/Line Receivers with Non- inverted 3-state outputs M402100BP - Crosspoint Switch Circuit - Dual 4x4 Crosspoint Switch

The first 3 are my prime suspects. Here's a pic of the board:

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Dave

Reply to
Dave
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Look for a to-92 package (plastic 3-legged transistor style) with UM66T19x on it. Pin 3 would be the output pin.

Reply to
Anthony Fremont

There are some TO-92 transistor like Melody Generators that have been used before in PABX's.

Like these

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Joe

Reply to
Joe G

You can probably find the music signal on the crosspoint switch with an oscilloscope or an earphone. You can use a 1k Ohm resistor and a

1uf capacitors in series to attach a CD or MP3 player. 8816 sounds familiar though. I think this is a remake of a Mitel chip:
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It could be a 8x16 matrix analog switch. Makes sense because a 4x4 crosspoint switch is not enough for a PABX with 8 lines.

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Reply to
Nico Coesel

I assume that the user manual (if you have one) doesn't give any information on whether or not the MOH function can be disabled by an instruction?

Other than that, it might be best to direct your query to the manufacturer in China

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Reply to
Ross Herbert

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