Contributed by Paul Fassbender.

August 1981.  Contributed by Steve Cichorsky.

Lesson XIII, Elementary Correspondence Course, Bell Tel. Co. of PA, Diamond State Tel. Co. 1952 view highlights 300- and 500-type phone circuits. Features of the "new" 500-type sets. Contributed by Paul Fassbender.

Identifying stations on key telephone systems (A-B-C, etc.)

Sample filled-in form used to document keyset characteristics.  Used to plan an installation, and as a reference for installers and repair techs.  Sets were identified with letters and numbers.  Letters on clear plastic number card windows (Form E-2959) are covered in BSP C37.321, I5, section 2.27.  Apparently there were "forms" from -A to -Z (except -I) with the corresponding letter on the disk (e.g. Form E-2959-A).

"At multi-station key telephone set installations, as in the 1A and 1A1 Key Telephone Systems or in 750A or 755A P.B.X. systems, etc., substitute these windows in the station number card holders for the regular windows ... to designate stations A, B, C, etc., in accordance with the work sheet data furnished with the service order.  Also refer to these letter designations when reporting station visits for either installation or maintenance reasons."

Scan is poor quality, as the original was a vintage photocopied form.  Contributed by Jeremy Walters

Extract from the 1918 Western Electric Electrical Supply Year Book catalog covering Interphone Systems.

Bell Labs Technical Memorandum 67-2623-2
Active RC-Tantalum Integrated Circuit Filter Design for High Performance
SPecifications - Part 1, 2/1/1967

Bell Labs Technical Memorandum 67-2655-11
An Electromechanical Filter Below 500 Hz, 5/3/1967

Bell Labs Technical Memorandum 67-4734-7
An Introduction to the Available Computer Programs and Other Design Aids
for the Design of Filters, Equalizers and Other Networks, 5/15/1967

Bell Labs Technical Memorandum 67-5311-18
Notes on the Design of Cosine Roll-Off Filters, 8/29/1967

Bell Labs Technical Memorandum 67-5316-1
Active RC Filter Building Blocks Using Frequency Emphasizing Networks -
Part 1, 1/3/1967

Bell Labs Technical Memorandum MM 67-5316-3
Realization of FEN RC Input Networks, 5/15/1967

Bell Labs Technical Memorandum MM 67-5316-6
Design of a Modified Raised Cosine Filter Using Hybrid Integrated Filter
Sections, 9/14/1967

Bell Labs Technical Memorandum MM 67-6323-6
Design Considerations for 50 db Bandpass Filter, 4/4/1967