PBX Music On Hold

[Dave]

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:
http://www.geocities.com/eigenvector_2000/IMGP1486.JPG

Dave

 

[Anthony Fremont]

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.

The first 3 are my prime suspects. Here's a pic of the board:
http://www.geocities.com/eigenvector_2000/IMGP1486.JPG

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

 

[Joe G]

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:
http://www.geocities.com/eigenvector_2000/IMGP1486.JPG

Dave

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

Like these
http://www.utc-ic.com/product/db/melody.php



Joe

 

[Nico Coesel]

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?

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:
http://products.zarlink.com/product_profiles/MT8816.htm

It could be a 8x16 matrix analog switch. Makes sense because a 4x4
crosspoint switch is not enough for a PABX with 8 lines.

 

[Ross Herbert]

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:
http://www.geocities.com/eigenvector_2000/IMGP1486.JPG

Dave

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 http://www.gzdlt.cn/doce/lxwm.htm