| Cover | Dec. 01, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Dec. 1, 2020 |
| Entity File Number | 001-31588 |
| Entity Registrant Name | COMMUNICATIONS SYSTEMS INC |
| Entity Central Index Key | 0000022701 |
| Entity Tax Identification Number | 41-0957999 |
| Entity Incorporation, State or Country Code | MN |
| Entity Address, Address Line One | 10900 Red Circle Drive |
| Entity Address, City or Town | Minnetonka |
| Entity Address, State or Province | MN |
| Entity Address, Postal Zip Code | 55343 |
| City Area Code | 952 |
| Local Phone Number | 996-1674 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value, $.05 per share |
| Trading Symbol | JCS |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
