33C audio connector and 1A1` system.

[Babybearjs]

OK guys! MERRY CHRISTMAS! today I have a 33C audio interface from a com-key system and need to know, where in my 1A1 system do I connect the audio input? (terms 3 and 4) does anyone know. I have a 202 and a 212 KSU that runs my 4 lines and I just need to know what terminals the MOH input goes on. anyone still running some 1A1 systems?

[Dave F]

1A1 systems generally don't support MOH, therefore there is no "official" place to connect the audio.  However, you can input the music across the line-holding coil of the H relay on a 202D or 230B KTU.  Run the audio through a small 1:1 transformer and use a couple of non-polarized capacitors (1 or 2 mfd) to isolate the phone line from your audio source.  See attached drawing.

It has been about 50 years since I last played around with 1A1, and your posting brought back a lot of memories.  I don't have much experience with the 212A KTU, so I don't know if this trick will work there, but it might.  You'll probably have to do a little BSP research to find out.

DF

[5415551212]

1A1 systems generally don't support MOH, therefore there is no "official" place to connect the audio.  However, you can input the music across the line-holding coil of the H relay on a 202D or 230B KTU.  Run the audio through a small 1:1 transformer and use a couple of non-polarized capacitors (1 or 2 mfd) to isolate the phone line from your audio source.  See attached drawing.

It has been about 50 years since I last played around with 1A1, and your posting brought back a lot of memories.  I don't have much experience with the 212A KTU, so I don't know if this trick will work there, but it might.  You'll probably have to do a little BSP research to find out.

DF

I have a 1A2 (not a 1A1) but and I used a 600 ohm audio transformer with a circuit like that to put music on my DP-1900 intercom line and it works great. 

[poplar1]

B.B. Wingo said he used to get crosstalk trouble tickets for lines in downtown Atlanta that had audible music in the background. He finally isolated it to a nearby AM gospel radio station whose engineer, after more than a few drinks, would go on the roof and turn the power for the antenna way past what the license permitted.

Putting a line on hold on a 1A2 system unbalanced the line, making the music even louder for callers waiting on hold. This was long before (if ever) the tariffs offered music on hold for leased key equipment in Southern Bell territory.

I remember hearing the click-click-click caused by the interrupter when calling a business  with 1A2, and getting put on hold. At least, you knew the call hadn't dropped. Definitely less annoying than newer systems where you had to hear repeatedly the initial greeting, because whoever programmed it didn't add the subsequent "please continue to hold."

[Babybearjs]

thank you guys for the help... I will try the H relay trick and see if that works...