sundance-communications.com/forum Forums General General Telephone & Systems Information 555 vs. 556

Just curious...

What is the difference between the 555 and 556 cordboards?

Thanks (again)

Joe

The 555 is a stand-alone, common battery PBX that can have up to around 20 trunks and 80 stations. It is used for businesses and hotel/motels.

It has a jack and lamp per trunk, and per station.

The 556 is essentially the same board, but is used as an attendant (operator's) position in conjunction with a dial PBX such as the 701. The cord units, attendant's talk/dial circuit, and basic wiring scheme are the same.

Since station lamps are not needed in an automatic PBX, it just has station jacks. Some of the 556 boards also had a row of alarm lamps, and a strip of registers at the top to allow studies of the traffic through the associated switch.

This is a 556. Note the lack of station lamps, and the alarm lamps and C/O keys at the top right.



This is a 555.

The earlier 551 and 552 boards shared the same relationship. The 551 was a stand-alone, and the 552 was the attendant's position for PBX's.

Hi Arthur,

Thank you for the info! I have a 555/556 frame and several odds and ends and just wondered about the difference. I have joined the TCI and ATCA listserve mail groups, and will be joining TCI shortly.

Gods, I am loving this phone stuff. Finally, my inner phone man is being recognized!

Best,

Joe