I just acquired a full 4A Speakerphone with 23A Block Connector. I have the M16c Cord and have ordered a 44A Conn Block. The question is where I go from there to connect to a Single Line? I wanted to take a standard phone line with modular plug on one end and wire it onto the 44A and connect it with the M16C Chord, but I have NO idea which color of the cable should correspond. I'm looking at the schematic but I haven't been able to identify the color code as of yet. Any ideas? This set has been hooked up before (not by me) and the wires that were used have the leads visible already. This set has everything.. Power Adapter etc... and is in fairly unused condition. I would love to get it back up and running but i need to some how make it modular. I noticed that there is a Red, Green Yellow cable in the 16C chord, but it doesn't look like they were used in the last hook up and the schematic doesn't show the red cable lining up with the Red cable from the phone.

Also.. although this is a 4A Speakerphone Same appearance, transmitter, speaker, etc.. It's not a "Bell" Branded version. It's a Precision Components brand which I believe was sold to smaller phone companies to install with key telephone systems in places where Bell telephone didn't exist But I'm assuming it will still work the same as the Bell branded version.

The 4-type speakerphone is intended to be used with a single-line telephone (model 500R/S or 2500S) or a 565HK or 2565HK multi-line set, or a x830-type set (10-button set).

It is not intended to be used as a stand-alone unit.

The 2500S is not the same as a 2500D. The S has extra TT dial contacts and a terminal board to attach the extra mounting cord leads.

The x565 sets have the appropriate dial and mounting cord leads.

According to the Diagram of the Western Electric 4A Speakerphone.. the Single line can be split at the 44A Conn Block where an additional single line goes off to the single line Telephone, and the 16C Cord goes to the 4A. Essentially the Speakerphone is a separate extension with this diagram. That's one diagram. It can also be connected directly to a single line phone as you are suggesting. I want to do it the first way and it's certainly possible as I've even seen it done before. You loose some functionality such as on hook dialing etc.. It's really a question of putting the correct leads in place. I just need help deciphering the leads from the diagram in the Single Line Instruction hook up.

I just wanted everyone to know that I finally did get my system up and running. For the record, It CAN be wired for a Modular connection. I used a simple wall Jack to complete it, but I had to cross the lead where the transmitter is waiting for the Telephone to send the connection that it's on the hook with the same lead that comes of the R2 Connector (Yellow or Also known as A1). This way it thinks the phone is always on the hook. It won't do On the hook dialing but everything else works fine. You can turn it on and leave it on while you dial on the phone without any feedback. When you hang up the phone it will resume connection.

Also, I did this with a type 4B speakerphone which is the precision components version, however, after comparing the schematics for both systems, it's the same procedure for the 4A. The only difference is the color of the lead cables in each set is different. If anyone needs help how to hook this up to single line without a 2500S or 500SM single line phone let me know.